# Throttle governed engine



## Brian Rupnow (Dec 18, 2019)

This is going to be something a bit different. Most of you will have a fairly good knowledge of how a hit and miss engine runs. On a hit and miss engine, the governor disables the exhaust valve when the pre-set rpm is surpassed, holding the exhaust valve open and letting the engine coast until the engine slows down, at which point the governor allows the exhaust valve to close and the engine will once more be able to build compression and fire.  However, there is a different way of governing an engines speed for engines which are not "hit and miss" types. In this type of governing, the governor opens and closes the butterfly valve in the carburetor to adjust the engine speed. In a perfect world, you "dial in" the speed at which you want the engine to run. If the engine speed slows beyond that point, a linkage from the governor opens the butterfly valve in the carburetor and admits more air/fuel mix to bring the engine back up to the "dialed in" rpm setting. If the engine rpm exceeds the "dialed in" speed setting, the governor closes the butterfly valve, thus starving the engine for fuel until it slows down to the dialed in rpm. I have a twin cylinder opposed engine that I built a few years ago, which has a manually controlled butterfly valve in the carburetor.  I also have a governor which was salvaged from the very first "hit and miss" engine which I designed and built. (The engine ran, but was horribly unbalanced). Over the course of the next few weeks, I am going to try and "marry" the two bits of technology to end up with a "throttle controlled" engine. Follow along. It should be interesting.---Brian


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## Brian Rupnow (Dec 19, 2019)

Since my twin cylinder engine is a few years old now, and has ran a lot, the first thing to do is to run a few diagnostic checks. The attached drawing and explanation will give a pretty good way to check the valves and rings on each cylinder.


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## tornitore45 (Dec 19, 2019)

Clever.  Why did not I think of that?  A false spark plug to connect the compressor.


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## Brian Rupnow (Dec 19, 2019)

So, now I have something to screw into the sparkplug hole and do my valve and ring testing. Now it's out into the blizzard to get my good wife some cold medicine from the drug store.


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## Brian Rupnow (Dec 19, 2019)

Testing the left side cylinder at 40 psi shows no leakage of either valve and no leakage at the piston. Now I will move over and test the other cylinder.


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## Brian Rupnow (Dec 19, 2019)

After checking the right side cylinder and discovering no leaking valves or rings, I went ahead and started the engine. It needs a bit of run time to clear itself out, but appears to be working okay. Tomorrow I will test the rpm range with my laser tachometer before starting any modifications to make it a governor throttled engine.


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## Brian Rupnow (Dec 20, 2019)

As with all things, the layout and development of something totally new may seem to look a bit "goofy". However, goofiness aside, the components all have to be modified and set up so it is physically possible to make and assemble them. I don't want to make any permanent changes to the twin cylinder engine, but realize that the governor may go thru some dramatic changes. At this stage of things, I have unbolted the fuel tank and set it aside, and sussed out an o-ring drive for the governor. From here I will move on to the linkage necessary to interface with the carburetor. I'm off with my grandson this afternoon to see the latest Starwars picture.


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## Brian Rupnow (Dec 21, 2019)

Well, here it is in principle at any rate. The "at rest" position of the carburetor throttle is normally fully open. As centrifugal force makes the governor balls swing out away from the stem-post, the center red rod moves downwards. This causes the blue assembly to tilt about the center of the hub (which is attached to the governor body with a shoulder bolt, not shown). This rotates the vertical governor arm, which is attached to the carburetor throttle with a link, and will bring the engine down to idle speed when the balls are fully extended form centrifugal force.  So---Any load imposed on the engine will make it slow down. This means that the governor arms will move in towards the center of the stem-post as centrifugal force becomes less, swing the vertical arm, and feed the engine more gas to counteract the load and bring the engine back up to speed.The threaded handle with the spring below it can be adjusted up or down to put more or less pressure on the blue linkage to counteract the centrifugal force, which determines at what rpm the governor engages. There is more to this, but this is the basic concept to get your head around.


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## cds4byu (Dec 21, 2019)

Briggs and Stratton engines use a slightly different governing arrangement.  Rather than having the governor push directly on the butterfly, they have the governor push on a spring connected to the butterfly.  The throttle control is also on a spring connected to the butterfly.  This allows the governor to work at various throttle positions, not just WOT.

I remember you using a similar arrangement on one of your hit and miss engines a while ago to enable you to better set the governed performance.  You may wish to do the same here.

Carl


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## Brian Rupnow (Dec 21, 2019)

There is a subtle bit of magic around that mechanical link between the governor arm and the throttle arm. It has to be a solid link in order to work and make the carburetor throttle arm move in concert with the governor arm.---But---when the engine is at rest and not running, the default setting of the governor is such that the carb throttle is wide open. These small engines are not fond of starting with the throttle held wide open. Therefore--That solid link must also be capable of being over-ridden so that when the engine is at rest and not running, the throttle arm can be held in the "idle" position so that the engine can be easily started. As I said, it is a subtle bit of magic. That solid link actually has to have a spring incorporated into it's design so that even though the governor is in the "wide open throttle" position, the over-ride can hold the throttle arm in the "idle" position. I will be addressing that issue and will post the updated solution when I get the design finished.


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## Brian Rupnow (Dec 21, 2019)

Well, I never said it was going to be easy---


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## Brian Rupnow (Dec 23, 2019)

Well Sir!!!--This governor controlled throttled engine isn't for sissies. I've rejigged things about four times now, trying to come up with a workable plan. A great thank you to George Britnell for giving advise on this. I can build practically anything, but it is nice if you have some certainty that whatever you build is going to work. I've been trying to comprehend what George is telling me, and scouring the internet looking for information on Briggs and Stratton engine mechanical governors. What you see here doesn't show the carburetor, only the throttle lever. One exhaust stack has disappeared, but only because it was going to interfere with my linkage. I am going to have to make a different shaped exhaust for this side of the engine.


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## Hobbyists (Dec 23, 2019)

tornitore45 said:


> Clever.  Why did not I think of that?  A false spark plug to connect the compressor.


In the mechanic field, it's been used for decades. It's called a leak down tester


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## Brian Rupnow (Dec 24, 2019)

Since the arc is just a tad to big to turn on my lathe faceplate, I will cut it out oversize and then drill a chain of 1/4" holes thru as shown, then cut it out on the bandsaw, then use my vertical oscillating sander to clean up the stubs of material left between the holes.


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## Brian Rupnow (Dec 24, 2019)

This went much faster than I thought it would. Of course when you have a cad system that gives you all of the ordinate dimensions, it's just a matter of turning cranks and watching the dro numbers. Merry Christmas to all of you guys and girls that may be following this thread.---Brian


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## Brian Rupnow (Dec 25, 2019)

Well Dang!! I'm impressed. Christmas is being celebrated a day late here because of various sons and daughters "in law obligations". This gave me a chance to sneak down to my machine shop and build the main governor body. A bandsaw, milling machine, and oscillating cylinder sanding machine makes short work of something like this.  The old guy with the white beard and red suit and bag full of presents will show up here tomorrow along with all of my kids, spouses and grandkids.


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## Brian Rupnow (Dec 29, 2019)

Moving forward things seem to be mounting the way I wanted them to. I am finished with the governor body main parts. Next up will be the linkage which connects things to the carburetor.


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## Brian Rupnow (Dec 30, 2019)

Today was governor linkage day. The brass lever is moved thru it's arc of travel by an internal rod that is acted upon by the governor weights. Yesterday when I mounted the governor body to the steel hoop around the flywheel/fan, I somehow got it as crooked as a dogs hind leg. So--Part of the day was used up dismounting it, lining it up correctly, and then drilling/tapping new mounting holes in the hoop.


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## Barnbikes (Dec 30, 2019)

I think it is cool looking. 
I just hope the belt does not come off. Keep your hand on the kill switch.


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## Peter Twissell (Dec 31, 2019)

If one wanted to protect against runaway in the event of a governor belt failure, a simple ignition switch could be arranged coupled to a belt tensioner, such that loss of belt tension would cut ignition.


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## Brian Rupnow (Dec 31, 2019)

This morning I made  the adapter which goes between the intake manifold and the carburetor, and the link which ties the governor lever to the carburetor throttle lever. I am not really sure what I'm doing here, and the more I do, the less sure I am. (That is not as unusual as it sounds!!). In the attached picture, my hand is holding the spring in tension, and the levers are pulled  into what is actually a "wide open throttle" situation. As the engine runs and centrifugal force makes the governor weights swing out away from the center, it actually pulls the throttle lever against the spring tension, until the carburetor is in an "idle" position. I have to adjust the spring tension to a point where the engine will settle in and run at 2000 rpm. but not so far that the engine idles. Now, if a load makes the engine slow down, the governor weights won't have as much centrifugal force, and the spring tension will pull the lever into a more "open throttle" position, causing the engine to run faster and bring the speed back up to the magic 2000 rpm.  So--The magic here seems to be my ability to adjust that spring tension so the engine runs at 2000 rpm but not any slower. However, that is only part of the equation. I also have to have the capability to completely over-ride the governor weights and bring the carburetor into a "full idle" position for starting. I THINK perhaps I need a counter spring pulling in the opposite direction to the spring I am holding, so that when it is engaged the carb throttle moves into a "full idle" position.


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## Brian Rupnow (Jan 1, 2020)

Update time---I really didn't want to cut the exhaust stack off on the governor side of the engine. Sometimes as I design and build these things, I see a way to change the design a bit and save myself some headaches. By brazing a piece of round 3/16" brass rod to the far side of the governor arm, I can move the spring over closer to the fan shroud to clear my exhaust stack. I have removed the pull cable and extra spring that showed up in a previous 3D model and went to a simple lever which I can move back and forth to determine the tension of the red spring. When I reach a point where the spring tension is strong enough to limit the motor rpm's to where I want them to be (about 2000 rpm governed) then I tighten the yellow threaded handwheel on the far side of the hand lever to lock it in place. I do have an idea for the mechanism that will completely overcome the governor and move the throttle into a closed position to make easier starting, but I have to chew on it for a while before I model it.


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## CFLBob (Jan 1, 2020)

Brian Rupnow said:


> When I reach a point where the spring tension is strong enough to limit the motor rpm's to where I want them to be (about 2000 rpm governed) then I tighten the yellow threaded handwheel on the far side of the hand lever to lock it in place. I do have an idea for the mechanism that will completely overcome the governor and move the throttle into a closed position to make easier starting, but I have to chew on it for a while before I model it.



For what it's worth, when I saw your post last night talking about this I started thinking of something with set screws to preposition where the lever is and keep it from going too far.  I was trying to visualize it when the holiday interrupted and then I promptly forgot.

Now I'm thinking something like the old automatic chokes we had on our cars.  A bimetallic strip to hold the throttle in a position that changes as the engine heats up.  

I think they worked backwards from what you want; they started wider open and then slowed down.  Aside from where to get the bimetallic strip (old heater/air conditioner thermostats used those, too), it doesn't seem that bad.

Reminds me of the sayin, "nothing is too hard for the man that doesn't have to do it."


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## Brian Rupnow (Jan 1, 2020)

Today seen significant progress on the governor control lever. I can loosen off the knurled handwheel and swing the brass lever into whichever position gives the best spring tension. The spring tension is what sets the "governed speed". I was able to position everything so that I didn't have to butcher my exhaust stack. I still have to work on a mechanism to over-ride the governor and set the engine throttle into it's "idle" position, as that is the best position when starting the engine.


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## G54AUST (Jan 1, 2020)

'Morning Brian.   (et al)

     Following this "marriage" thread with interest.     Nice engine.   The fan/flywheel is very reminiscent of a Volkswagen beetle donk.   Is it base on a VW ?   (half VW = \U ???)

     Did you do a thread build when constructing this engine ?



Kind Regards,

Trevor,
Melbourne,  AU


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## Brian Rupnow (Jan 1, 2020)

Hi Trevor--I did a build thread on this engine a few years ago, and I do sell a complete 70 drawing set of plans for $25 Canadian funds. It is not based on a VW. I just wanted to arrange the fan blades so they blow a continuous stream of air across the cylinders. It will run all day without overheating.---Brian
https://www.homemodelenginemachinist.com/threads/opposed-twin-i-c.24899/


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## G54AUST (Jan 1, 2020)

Hey Brian.

Many thanks for such a quick reply.

What format are the plans in,  printed hard copy,  PDF,  memory stick ?   Other drawing sets ???

Twenty five maple leaves is a most reasonable price.

I'll have a good look at your thread …..


Kind Regards,

Trevor,
Melbourne,  AU


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## Brian Rupnow (Jan 1, 2020)

My plans are sold as pdf files.---That way you don't need any special software to open and view them. I have sold plan sets quite literally "All over the world", many in Australia and New Zealand.---Brian


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## Brian Rupnow (Jan 2, 2020)

Now we are in the final phase of this throttle governed engine. As it sets, two things are happening. With the engine setting at rest, not running, the single spring pulls the throttle on the carburetor wide open. When the engine is running and the governor weights fly outward, that puts tension on the spring and pulls the throttle into a closed position, but not all the way closed. I adjust the tension on the single spring to a point where the engine is running at 2000 rpm., which is close to the idle position, but not too close. This is a state of equilibrium between centrifugal force from the weights and the tension of the spring. Now there is only one issue left. These small engines are difficult to start when the throttle is "wide open".  Now I have to devise an "over-ride" that will pull the throttle to the fully closed (idle) position for starting, but not effect anything else in the governor train. Once the engine starts and warms up in the "idle" position, I disengage this "over-ride" and the governor takes over to control the speed of the engine.--3D cad to follow---


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## Brian Rupnow (Jan 2, 2020)

This is the mechanism which over-rides the throttle spring and moves the throttle lever into "idle" position for start up. The pinkish colored bar has a slot in it that fits around the throttle lever. It is all clearance except for the left end of the slot. This bar moves left or right, and is held in position by a ball detent screw (yellow). It rides in a guide which is bolted to the main governor tower.  So--In the current model, the engine is stopped, the balls are in against the stem post, and the pinkish bar has been pulled to the extreme right and is held there by the ball detent screw. The left hand end of the slot is touching the throttle lever to pull it to the extreme right which is the idle position. The engine is started in this position, and allowed to warm up. Once the engine is warmed up, the pinkish bar is moved to the left, and no longer touches the throttle lever. At this point the governor takes over control of the throttle. The pinkish colored bar no longer touches the throttle anywhere.


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## G54AUST (Jan 2, 2020)

'Morning Brian.

PM sent.

Regards,

Trevor,
Melbourne,  AU.


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## awake (Jan 2, 2020)

Nice solution. Eager to see it in action!


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## Brian Rupnow (Jan 2, 2020)

I  will be "truly Impressed" if this system comes together like I'm imagining. I know that every sub assembly that I design works. I have built them before, and they worked. The big trick will be getting them all to work in harmony with each other. I know that similar full size machine assemblies work exactly as I want the model to. Best similar thing I remember was a local sawmill ran by a Caterpillar six cylinder diesel. It ran at a fast idle when the mill wasn't operating. As soon as the power was coupled to the stationary mill machinery, the engine would immediately kick up the throttle. It didn't run any faster, but the exhaust sound changed quite dramatically---You knew by the sound that it was working. Then when they put a 20" white pine log on the carriage and ran it through the saw, the engine would really start to blatt. It wasn't running any faster, but you knew by the sound that it was putting out tremendous power to keep the rpm's from dropping. After the log went through the main-saw, you could again hear the difference in the noise of the engine as it throttled back. It was all done mechanically, no human involved on the throttle controls. If I can do that on the scale I am working at, then yes, it's going to impress my socks off.---Brian.


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## Brian Rupnow (Jan 3, 2020)

Last night we had 4 year old grandson for a "sleep-over". He's a great little kid, but it didn't leave grandpa with a lot of machining time. I did manage to get the main idle bracket machined and installed. It is a rather complex shape, but turned out very well. I only have about one day of making parts left, and then I will see if all of these add-ons actually work. You would think that with all of the O-rings that I bought for the edger and then didn't use, I should have one that fits this application.---I don't. Everything I have is either too short or too long. Monday I will get on the phone and order one which fits this beastie.


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## Brian Rupnow (Jan 4, 2020)

Okay boys and girls--we have a lot going on here. In the first picture, engine is stopped, governor over-ride pull knob is pulled to extreme right, which overcomes the tension spring and pulls the carburetor throttle lever into closed/idle position so the engine can be started. I didn't have a ball detent screw, so I made up a knurled and threaded brass knob which sets where the detent screw would have gone. I pull the governor over-ride to the extreme right and tighten the knurled brass knob so it stays there while I am starting the engine. Second picture shows the over-ride pull knob released, and the tension spring pulls the throttle to the wide open position. This is a situation that should normally never occur, because as soon as the engine starts, the governor balls will "fly outward" and pull against the tension spring, moving the carburetor throttle lever into a position which is actually quite close to the "idle" position. (if the engine were running, I would set the spring tension so the governor weights and the tension spring reach equilibrium at about 2000 rpm.) The third picture shows my hand holding one of the governor weights in it's "fly out" position, and you can see that the governor pulls the throttle lever back close to the idle position. That governor over-ride bar has an over-size clearance slot in it, and only contacts the carb throttle lever when it is pulled into the "engine start" position.


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## Brian Rupnow (Jan 5, 2020)

When I first built this engine a few years ago, I machined a steel starter hub which attached to the end of the crankshaft to engage with my electric drill for starting. Then I discovered that the compression was so high that I couldn't comfortably grip the starter hub in my hand to turn the engine thru it's different stages to set timing, etcetera. No problem--I just machined a larger diameter piece from aluminum, knurled the o.d., and Loctited it to the outside of the starter hub.  The other end of the crankshaft isn't available for a power take-off pulley, so now I am going to rework the started hub so that it will keep the knurled profile for a hand grip, but also become a power take off pulley.---Brian


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## Brian Rupnow (Jan 5, 2020)

In this picture, the starter hub and knurled aluminum ring have been removed from the engine and separated. They were only loctited together. A new intermediate  hub has been turned and knurled, and will replace the old knurled aluminum ring but will still incorporate the inner hub.


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## Brian Rupnow (Jan 5, 2020)

And finally, there's my baby with the new starter hub-pulley installed. Room on the pulley for two 1/8" O-rings.


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## Brian Rupnow (Jan 6, 2020)

Any time you take an existing engine and "repurpose" it to a different style, as I am doing here, some things get a little weird. This engine was designed and built with a manually controlled throttle, and now is being changed over to a governor controlled throttle. All of the new parts are made and installed, but I still need to mount the gas tank somewhere. It has to be marginally lower than the center of the carburetor, it must be away from the exhaust pipes, and the gas tank outlet still has to exit in the general direction of the carburetor. Playing around with the 3d cad model, I have found a position that meets all of these requirements and only requires that I make up one new plate and mount it to the steel bracket that holds the ignition coil. Looks a bit weird, but it works. This uses the original gas tank with no changes to it at all.


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## Brian Rupnow (Jan 7, 2020)

This mornings work involved a new bracket to mount the gas tank, and a new, rather squirrelly looking yellow gas line. Gas tank and line clear all moving parts, avoid being close to exhaust stacks , and tank is marginally below centerline of carburetor. And that's it!!! I ordered a couple of new O-rings to drive the governor from the rear of the flywheel, and once they arrive we will see if this thing can fly---


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## Brian Rupnow (Jan 8, 2020)

You may remember that I made up a narrow 1/16" wide knurling roller to put a knurled finish in the bottom of o-ring slots on the pulleys I make. This was in order to keep the pulleys from slipping as they drove an o-ring used as a drive belt. I haven't used it before, but this morning I decided to do both driver and driven pulleys on the governor drive. this is what the knurled slot looks like.


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## Brian Rupnow (Jan 8, 2020)

How exciting!!! I have the engine running and the governor is operating and very sensitive. I haven't got things to the point where they are consistent enough to make a video, but it works.  The engine is not terribly sure that it likes the additional load put on it by the governor system. I can take the o-ring drive off, and the engine runs quite fine. I put the o-ring belt back on, and the engine wants more throttle to run with the additional load. As it is running, I can see the governor weight system moving in and out against the tension spring and moving the throttle, seeking it's "happy spot". I have my office door open to keep from gassing myself, and it's colder than a witches tit in my office. Going to quit now and have some lunch, and try to get the grin off my face.


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## dnalot (Jan 8, 2020)

Looking forward to seeing the video. I hope to die with a grin on my face. 

Mark T


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## Brian Rupnow (Jan 8, 2020)

A couple of short videos. I'm not finished yet, and there is a blizzard raging outside my office door, so I can't run the engine very long without having my door open. The fact that the engine runs and the governor is trying to do it's thing is quite positive. I am expecting to have better results as I refine things a bit. There is more governor action in the first video clip than in the second. I think I had the governor locked in position on the second run.


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## Brian Rupnow (Jan 8, 2020)

Okay, third times a charm, and this is probably where I will quit for the day. The governor is working and controlling the throttle on the carburetor. I'm sure I have more tuning to do, and that arm which holds the end of the tension spring is going to need an arrangement to make it far more adjustable. I have to think on that one for a bit.--Probably need to make it adjustable with some kind of threaded screw to get fine adjustment. At any rate, concept is proven, and I like it.


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## Brian Rupnow (Jan 8, 2020)

I probably burned up a few brain cells thinking of this--I want to turn the red threaded knob to move the green threaded rod to tension the spring---but I don't want the green threaded rod to turn. If I put a flat on each side of the threaded rod, and a slot instead of a round hole in the beige colored bracket, that should do it. This will let me fine tune the tension on the spring to give correspondingly finer tuning of my target engine rpm.


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## Brian Rupnow (Jan 8, 2020)

And---On the weirdness-ometer-- I seen a dog wearing snow boots today. There is a foot of snow here, and it was a rotten day outside, so I went up to the Georgian shopping mall for my "fat man's walk". (Four laps around the mall=1.6 miles.)  People take service dogs in training up to the mall. I seen a half grown German Sheppard dog, wearing a dog coat (I've seen dog coats before) and a set of pretty blue snow boots!!! I commented on it to the trainer, and she told me that "All the dogs are provided with snow boots in inclement weather." The dog didn't seem to mind the boots at all!!!  Hey---I want to live another seventy three years---I'm still seeing new things that I've never seen before.


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## Brian Rupnow (Jan 9, 2020)

This morning I built the fine adjustment bracket and flat sided 1/4" threaded part exactly like the 3D cad and it all works fine. I re-used the knurled nut? that originally held the first spring tension lever in place. Now I'm at a point where there is nothing more to make. Now it gets down to the hard part of making it all work in harmony. I shouldn't admit this, but I enjoy making the parts way more than actually getting everything to work. I have a fairly good success rate of getting things I design to work, but there are times when I wish I had George Britnell and Chuck Fellows standing here in my office to bounce ideas off of. Getting small engines to perform is 70% engineering, 20% experience, and 10% magic. Probably tomorrow I will take the drive belt off of the governor and set the engine up to run as well as it can without the governor. Recheck the ignition timing, the valve timing, and the carburetor needle  settings. Once I have worked thru that, I will put the governor drive belt back on and make any necessary adjustments.


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## Brian Rupnow (Jan 10, 2020)

I'm feeling a bit under the weather today, so no real work, just a lot of heavy thinking. George Britnell had mentioned that these small engines don't really like to start with a wide open throttle, and I agree with him. That is why I made the sliding affair with the pull knob that could be used to over-ride the governor and lock the carburetor in it's "closed" position for starting. However---I have found that when cranking this engine with my electric drill that the governors are very sensitive and as soon as I start to turn the engine over, the weights fly outward and put the carburetor into "closed" position anyways. Although this style of carburetor does have an internal "idle adjustment screw" which actually limits how far the throttle closes it is giving me problems. Without changing the complex bracket that holds this sliding affair with the pull knob, I can replace the bolt on top-cover and have room to install a 1/4" threaded rod with a knurled end on it to act as the throttle stop. This will actually work against the throttle lever arm, instead of being part of an internal throttle stop. I have a good view right down the carburetor throat the way this carb is mounted, and much better accessibility to adjust the throttle stop to a point where the engine idles but doesn't die out and stall. (The carburetor is hidden in this view, with only the throttle arm being visible).


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## Brian Rupnow (Jan 14, 2020)

I have made the changes outlined in the last post. Engine runs, but not happily. I am in the middle of removing the home made carburetor and putting on a purchased Traxxas carburetor. This is more of a quick and dirty diagnostic than anything. Self throttling feature will not run with Traxxas carburetor, however if the engine runs well with the Traxxas, then I know the home made carb isn't working properly. If behavior doesn't improve, I will have to dig deeper. The videos on Youtube had the links pasted in this thread. The Traxxas 4033 carburetor is just about the perfect size for large single (1" bore)and smaller (7/8" bore) twin cylinder engines. If I have any complaint at all about them, it is the fact that the side which attaches to the intake is a plain 10 mm outside diameter. This means that any time you want to use them, you have to make a simple adapter like the one shown here. I use a bit of 638 Loctite to attach the carb into a reamed 10mm hole in the adapter. I'll let the Loctite dry overnight and see what happens with the engine tomorrow. The governor has been disconnected by slipping the o-ring drive belt off the engine pulley.


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## Brian Rupnow (Jan 15, 2020)

The engine did run with the Traxxas carb on it, but it didn't run consistently. I discovered it had a plugged gas line right where the line enters the gas tank. Even after I had cleaned out the blockage it wouldn't run consistently. Finally, I tore the engine down completely. I was really trying to avoid that, but ya do what you have to do. I decided that first order of the day was to replace the viton O-rings. I don't think they were the problem, but since I have everything apart that is what I will start with. The two old rings are on the left of the picture, the two brand new ones on the right. In case you were wondering---I hate this worse than snakes!!! I like to build an engine, tune it, run it, make a video of it, then move on to something else. This going back and conducting a post mortem on an engine which no longer runs the way I want gives me a big pain in the head.


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## Brian Rupnow (Jan 15, 2020)

Engine has been reassembled with new rings. This complete disassembly has given me a chance to clean everything up and to get rust and crud off the fins of the cylinders. I found that the set screw holding one wrist pin in place had fallen out, but fortunately the pin hadn't drifted sideways and scored the cylinder wall. I don't use aluminum outer cylinder with a cast iron liner. I make the entire cylinder from one piece of cast iron. That way it is much less work, better heat dissipation, and all I sacrifice is a bit of pretty. Tomorrow as I reassemble things I will check valve and ignition timing. The engine is so clean and new looking now that it is rather startling.


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## Brian Rupnow (Jan 16, 2020)

I may have found the culprit. The old rings were worn, but not to the point where the engine was losing compression, so they were probably doing their job just fine. However, as I proceed with the re-assembly, I have found that the adjuster for the intake valve on the right hand cylinder bank was way, way out of adjustment. It had backed off to the point where just the very tip of the cam was "grazing" the lifter. I had labelled the push-rods as I disassembled the engine, so they haven't been mixed up. I will reset all of the valve adjusters now.


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## Brian Rupnow (Jan 20, 2020)

An update---I have hit the wall on this engine, for the moment. I have replaced gaskets, set and reset valve and ignition timing, replaced rings, replaced carburetors, and tested every individual part. Every member of the choir sings perfectly, but I can not get them to sing in harmony. This doesn't happen to me very often. I can't even get it to run with all of the self throttling apparatus disconnected. I haven't been able to identify anything specifically wrong with the engine, other than the fact that one valve adjuster was out by a fair bit, but even with that valve clearance readjusted, it refuses to run. When I turn the engine over by hand with the cylinder heads removed, it will put a good suction on my thumb which doesn't fade away, and gives a distinct "pop" when my thumb is removed. The gas lines are clear, and fuel will run from the hose when I remove it from the carburetor. The vent hole in the gas cap is clear. I have adequate spark at both plugs. engine spins freely with heads removed--no hard spots. Only thing left to do is remove the ignition points, starter hub, and brass gear cover so I can have a good look at the timing gears. Thank you for your patience.---Brian


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## Brian Rupnow (Jan 20, 2020)

This is one of those one of those "unexplained mysteries" that you read about in the National Enquirer. I've got the poor old girl stripped right down to her undies now, having just removed the starter hub, ignition points, and brass gear cover. One of the things that I just discovered which doesn't affect the engine (I don't think)---I pulled up the detail drawings of both gears to see what I used to hold them to the crankshaft and camshaft---and found nothing!!!--I never added the set screws to the detail drawings back when I originally built this engine.  This is a bit strange, since I've sold half a dozen plan sets for this engine, and I have never had a call nor email asking about it. Next step will be to ensure the valve timing (valve beginning to open X number of degrees before tdc or bdc depending on which valve we're talking about). My software can let me set things exactly where they should be, degree wise, and then give me a linear distance from the top of the piston to the top of the cylinder. It doesn't appear that either gear has slipped from it's appropriate position relative to the shaft it sets on, but I will check it anyways. This is about as close to the "beginning" that you can get when doing engine forensics.


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## Brian Rupnow (Jan 20, 2020)

I have everything torn down to the bare essentials. I'm checking valve timing as we speak. Ignition cam is off the engine right now. Will reset everything as I build the engine back up.


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## Brian Rupnow (Jan 21, 2020)

This set-up lets me know exactly when the cam lobe begins to contact the lifter. I rotate the crankshaft slowly by hand in the direction it normally turns, and as soon as the cam contacts the lifter, the needle on the dial indicator moves. At this point, I measure from the top of the cylinder down to the top of the piston. My software tells me that when the piston is 0.263" from the top of the cylinder, the rotational aspect aspect of 15 degrees before top dead center has been reached. Since I am leaving approximately .010" of valve lash, that figure will closer to 2.53" before the valve begins to move.  Checking the actual distance with my Vernier caliper I measure .280"  This is well within the range of acceptable, but since I have everything apart I will loosen of the cam gear and reset it to exact numbers. All of the cam lobes are 'fixed" to the camshaft, so any change I make now will affect al of the valves in the system.


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## Brian Rupnow (Jan 21, 2020)

Okay--Something is a little hinky. Based on the intake valve having a lead of 15 degrees before tdc, the dimension from top of cylinder down to top of piston should be 0.253" which includes the valve lash of about 0.010". I have reset the left side of the engine to agree with this,(It wasn't very far out) and that automatically sets the right bank the same. However, the exhaust valves should have a 40 degree lead before bdc, which gives a dimension from top of cylinder down to top of piston of 0.894". I measure 0.710" which means a lead of 60 degrees which is 20 degrees too much. All of the four cam lobes are Loctited to the camshaft, which is an acceptable method of cam building. I now have to check the cams to generate real numbers instead of working with theoretical numbers and see what's going on.


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## Brian Rupnow (Jan 21, 2020)

The theoretical cam has 120 degrees of movement in the area which lifts the tappet. This translates to 240 degrees of crankshaft movement because of the 2:1 ratio between the crankshaft and camshaft. 240-180=60 degrees of movement which gets split between valve lead and valve lag. Theoretical split is 15 degrees before tdc. and 45 degrees after tdc. Real cam as measured with dial indicator has 130 degrees of  movement affecting the tappets. This translates to 260 degrees at the crankshaft. 260-180=80 degrees to be split between lead and lag. 80 -15 degree lead=65 degrees of lag. 65 degrees of lag translates to measurement from top of cylinder down to top of piston of .706" and actual measurement on engine e is 0.710". This tells me that cams have not slipped rotationally on the camshaft.


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## Brian Rupnow (Jan 21, 2020)

Tonight everything is back together. Ignition timing has been reset, Cylinders have again been pressure tested, and gaskets are all in place, nothing leaking that I can see. Liquid dish soap has been flowed around the cylinder heads while under pressure, and we have no bubbles to contend with, which pretty well assures no leaking head gaskets. Valve lash has again been adjusted. While I had the intake manifold off I gave it the old "Blow your guts out test" just to make sure there wasn't a big blob of gunk in one of the legs blocking the flow. Did I really see anything that would have prevented the engine from firing or running?--No, not really.  Tomorrow we will try to start this thing again.


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## LorenOtto (Jan 21, 2020)

Brian Rupnow said:


> Tonight everything is back together. Ignition timing has been reset, Cylinders have again been pressure tested, and gaskets are all in place, nothing leaking that I can see. Liquid dish soap has been flowed around the cylinder heads while under pressure, and we have no bubbles to contend with, which pretty well assures no leaking head gaskets. Valve lash has again been adjusted. While I had the intake manifold off I gave it the old "Blow your guts out test" just to make sure there wasn't a big blob of gunk in one of the legs blocking the flow. Did I really see anything that would have prevented the engine from firing or running?--No, not really.  Tomorrow we will try to start this thing again.


Brian, I admire your persistence.  I would have long ago abandoned this project as a lost cause.  Your will to continue will inspire me to do likewise.  Loren


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## Brian Rupnow (Jan 21, 2020)

Loren--I try to "Never give up."  It takes me to some strange places, but I solve a few mysteries.  It makes me crazy when things defy logic and reason. I may have discovered something this evening. On a conventional 12 volt coil and points, it doesn't matter which way you hook up to a 12 volt battery, it will still work. This dual output snowmobile coil I'm using may possibly be different. I decided to put the charger on my 12 volt battery tonight, and discovered that I had the battery hooked up backwards. I wasn't really happy with the size and strength of the spark the coil was giving. Instead of a fat blue spark at the plugs, it was giving rather anemic yellow sparks. Tomorrow I will hook the battery up correctly and see if the spark quality improves.


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## dsage (Jan 22, 2020)

Brian:
You might consider a different approach to  observing your valve timing.
With your cad program make yourself a paper strip with numbers from 0 to 360 around the circumference of your flywheel (length pi x D) (marking each degree).
Fasten it around the flywheel with zero across from a stationary line on the block at TDC.
Apply a few pounds of air pressure into the spark plug hole with a hose and screw in adapter.
Rotate the flywheel around until you hear the air start to leak from the intake or exhaust as the case may be and take a degree reading on the timing tape.
Same process for the valve closure (when the air stops leaking). Quite a bit more accurate than all your math and measurements to get the "actual" timing and no disassembly required.
Also a good check for valve leakage and ring leakage.


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## Brian Rupnow (Jan 23, 2020)

Yar Bugger Billy!!! We're up and running again. What a mad thrash it's been. I tore everything down to the bare chassis, checked the valve timing, then on reassembly I reset the ignition timing. When completely reassembled, still no joy. I had spark, I had fuel, but engine wasn't firing. As a last result I unbolted the left hand cylinder head, relapped the valves and made a new head gasket. This was very encouraging. When cranked I had fire in the left hand cylinder and smoke rings coming out the stack, but still not running. Then I pulled off the right hand cylinder head and done the same thing on that bank. There was more to this than it seems, because it involved retapping a few holes and making up some more specially shortened bolts. Finally I was rewarded with a running engine. Turn up your speakers. I do some "voice over" in the video, but the engine is noisy. Now that engine is up and running, I will do some fine tuning before I put the throttle governing governor back on. the engine. The video is crappy but I will make a properly lighted and sound controlled video after the fine tuning is completed.


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## Brian Rupnow (Jan 23, 2020)

Re--Getting engine to run:: If I had pulled the heads off and lapped the valves a bit more FIRST I probably wouldn't have done all the other things. When an engine runs well and gets put up on the shelf for a few years, then doesn't run properly when you get it down off the shelf, you start eliminating possible causes. The engine had spark. The engine had fuel. The engine refused to run properly. I pressure tested both cylinders with compressed air thru a fitting screwed into the sparkplug hole, and  they seemed to hold pressure adequately. I did every "easy" thing that I know how to do to make the engine run properly, and none of them worked. At that point it was either abandon the project or start digging deeper. For whatever reason, this engine seems to be very very particular about the valves sealing 100%. Ah well, it's January and I don't have a whole lot going on anyways.---Brian


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## Brian Rupnow (Jan 25, 2020)

I have restored the hand built carburetor to the engine, and it is running much better. I have decided that the engine would benefit greatly if I were able to manually adjust the ignition timing while the engine was running. The points will now mount to the red plate with the red handle. The red plate rotates on a central boss on the gear case, and by loosening the green capscrew I can advance or retard the timing to find the "sweet spot" where the engine runs best.


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## Brian Rupnow (Jan 26, 2020)

I had three grandchildren sleeping over and a sick wife, so I've been running around like a chicken with it's head cut off today.--Did manage a couple of hours this afternoon to whittle out the "Timing plate". The points shown are an old pair that I keep on hand for "set-up" purposes. The brass bit in the center will actually be attached to the front of the brass gear cover. When I have the handle attached to the timing plate, this will allow me to tilt the plate in one direction or the other, to the limits of the curved slot, to adjust the timing while the engine is running.


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## Brian Rupnow (Jan 27, 2020)

Here we have the timing plate and handle installed on the engine. The concept is that you set the ignition timing as close as possible with the plate mounted as shown in its neutral position.Then, when the engine is running and warmed up, you loosen the bolt that is in the curved slot, and this lets you rotate the plate and points mounted to it a few degrees clockwise or counter-clockwise. This retards or advances the ignition timing until the engine is running in it's "sweet spot", then lock down the bolt in the slot.


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## werowance (Jan 27, 2020)

i like the addition of the easy adjusting points.


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## Brian Rupnow (Jan 31, 2020)

I haven't ran of with the gypsies, nor anything nearly as exciting. I've been plugging away on this engine, correcting faults and trying to get my head around a few things. Like Bob Seger's song, "Nightmoves" I've been "Working on mysteries without any clues." I've had everything apart right to the bare bones and built it back up again, checking clearances and tolerances. I have no problem starting and running the engine. The problems are inconsistencies in the way it runs each time. Some of the new features I've added cascade. I added the manual ignition timing plate and lever, and it works fine---but it eats up 1/4" of clearance on that side of the engine. The answer to that of course, was a new pulley and starter hub, with an annular slot on the engine side 1/4" deep to fit over that #10-24 bolt head that holds the ignition points in place. I have eliminated everything that would potentially cause a problem except for the cams themselves. They are a direct copy of the cams Malcolm Stride used on his "Bobcat' and "Jaguar" engines. I made the single cylinder "Bobcat" engine with enough changes to rebrand it the "Canadian Cub", and although it ran satisfactorily it also shot vapour out the mouth of the carburetor while running. I ordered a new set of "Rimfire" sparkplugs yesterday from Roy Sholl at S & S Engineering.  If I decide that the duration of the cams is too great and is causing the vapour discharge from the carburetor, I'm not sure if I will go so far as to make new cams or not. When I first built this engine, I didn't put any key in the starting hub and crankshaft on that side of the engine. The engine ran so well and with so few problems that I thought I would get away with it. Of course, it has came back now and bit me on the arse, because with all the messing around trying to change this engine over to  a "Throttle governed" style, the starter hub was slipping on the crankshaft.  So, this morning I broached a keyway into the starter hub and set the entire engine up on my mill table with the crankshaft locked against rotation and milled a new keyway into the exposed end of the crankshaft. The saga continues-----Brian


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## Brian Rupnow (Feb 6, 2020)

Today we have some good news and some bad news. The good news is that the trouble with the right hand cylinder was indeed the sparkplug. I haven't got my new plugs from Roy yet, but I did discover a 1/4-32 sparkplug in one of my other older engines and used it to replace the sparkplug in the right-hand bank. The engine now runs fine. Who knows!!!---It might have been the bad sparkplug that was the problem all along. The bad news is that the engine doesn't want to accelerate while under load. The governor and linkage works exactly as I had planned. When I spin the engine over with my electric drill, the governor weights immediately fly out, closing the throttle right up to the adjustable "stop", the engine starts, and everything runs fine. When I put a load on the engine, the governor reacts exactly as I had planned. The engine slows down, the tension spring pulls the weights of the governor back to center, the linkage opens the throttle. BUT--then the engine stalls. If I engage the load very slowly, sometimes the engine will keep up, but nine times out of ten the engine just stalls out and quits. I more or less know why, but I'm not sure what I can do about it. In a conventional "old style" automobile with a carburetor, when you step on the gas to open the throttle, the accelerator pump squirts a stream of gasoline directly into the carburetor throat to keep the mixture from "leaning out" which would cause the engine to stall. In my miniature carburetor, there is no provision for an "accelerator pump". If I richen the mixture to my carb by unscrewing the needle valve, the engine won't run at low rpm. If I start the engine under load, it will run, but it doesn't like it. The vapour coming out of the carburetor throat has lessened considerably, so that may have just been a function of running too rich and having a bad sparkplug.


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## Cogsy (Feb 6, 2020)

Maybe it could be as simple as increasing the RPM that you're trying to run at? Of course you don't want it flat-chat or the governor would be redundant, but maybe running a bit higher in the rev range will give it a bit of extra time to 'catch up' before it stalls out and probably a bit more usable power as well.


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## 74Sprint (Feb 7, 2020)

I have quite a bit of time on RC engines, your carb appears to be one you have made. I would recommend 1. using a RC engine carb. 2. Use one with a smaller throttle bore, this will keep the air velocity up and more sensitive to throttle plate opening changes. 3. On RC motors if the throttle response is not there then we run a hose from the muffler (just before) to the fuel tank and use the exhaust pressure to help push fuel to the carb. This way it is a hybrid fuel injection system and helps to eliminate throttle stumble. Most RC carbs can handle going from alcohol to gas with no problems.

Ray


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## Brian Rupnow (Feb 7, 2020)

I have switched carburetors and am using a 4033 Traxxas Pro 15 carburetor now. I'm still having problems with the acceleration under load.


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## jeff.gearing (Feb 8, 2020)

I used to run Traxxas Uk until retirement around 10 years ago. I retained a load of spare parts including IC engines and bits. If you need anything for experiment with just let me know


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## jeff.gearing (Feb 8, 2020)

Oops, should have realised you were in Canada, I guess sending parts across the ditch is a bit of a waste of time. Sorry about that.


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## Brian Rupnow (Feb 8, 2020)

Jeff---Ahh well, a nice thought anyways.  4033 Traxxas are my "Go to" carburetor on most of my 1" bore engines. I have about a dozen of them. Right now I'm looking at building a choke for the one in this thread.--Brian


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## 74Sprint (Feb 9, 2020)

Brian Rupnow said:


> I have switched carburetors and am using a 4033 Traxxas Pro 15 carburetor now. I'm still having problems with the acceleration under load.



Brian, have you considered using the exhaust pressure to help feed the fuel?

Ray


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## Brian Rupnow (Feb 9, 2020)

No, I haven't considered using the exhaust gas to force the petrol up to the carburetor. I know that they do that on two stroke model airplane engines, but I've not seen it done on a four stroke stationary engine. This morning I designed and built a choke to see what effect it has.---Brian


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## Brian Rupnow (Feb 9, 2020)

I think I am going to "throw in the towel" on this project. I've spent two months working on it, with a few successes, but more failures and I've nowhere more to go on it. I will still wait until I get my two new sparkplugs from Roy Sholl and try the engine with them, but if I don't see a world of improvement, I'm going to call it quits. It has been an interesting but frustrating project, but I haven't been able to make it work the way I had hoped. Ah well, nothing ventured, nothing gained. I will offer this word of advice---If you design any kind of i.c. engine, don't put the sparkplugs at the bottom of a horizontal cylinder. I run a bit of two cycle oil with my naptha gas fuel to lubricate the Viton ring, but what I'm finding is the oil separates out in the cylinder and constantly fouls the sparkplugs. These engines don't run hot enough to burn the oil when running at low rpm. Thanks very much to everyone who has followed along.---Brian


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## Brian Rupnow (Feb 10, 2020)

Okay--I spent the morning on a redesign of the cylinder heads. IF I decide to go ahead and do this, it would move the sparkplug up to a point above the centerline of the cylinder. It would mean new heads, and everything in them. That is a lot of work.--Then again, I don't have a lot of other stuff going on. The only thing that makes this a somewhat attractive notion, is that I have all the material here to do it without having to buy anything. I will think on this for a while---


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## awake (Feb 10, 2020)

I knew it - when you said you were throwing in the towel, I just knew you would not be able to let it go.


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## bluejets (Feb 10, 2020)

Reading back through the last couple of pages and just wondered what overlap you have on the cams.
Fuel misting back out through the carburettor is normal on some engines at low revs but usually clears as the revs get to a more normal level.
That said, increased overlap can create problems in this area as well as the duration you previously mentioned.
However they would need to be rather "wild" grind to get this effect from duration.
Common is around 110 degrees.
Also with reference to your ignition, for one, the polarity of coil to battery is an important factor.
Aside from that, not having a blue spark with points and kettering system is an indication of a crook condenser.
Other factors aside, once then engine is running, it doesn't really matter where the plug is located.
There are radials which cope quite well to having plugs at the bottom.


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## Brian Rupnow (Feb 10, 2020)

The duration on the cams in this engine are 120 degrees.


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## Brian Rupnow (Feb 10, 2020)

After posting the previous 3D model, I went up to the mall for my "fat mans walk". As I walked along (four times around the mall is 1.6 miles) I was running thru this design in my head, and realized that the axis of the rollers that contact the top of the valve should be parallel to the rocker arm pivot pins. so--A slight change to the shape of the rocker arms corrects that issue, and actually makes for a simpler rocker arm.


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## 74Sprint (Feb 10, 2020)

Here's another thing to consider Brian is that a lean mixture is harder to ignite than say stroich so a stronger spark or less plug gap is needed. Oh by the way my 4 stroke ASP 0.65 RC engine uses exhaust pressure to the tank so it's just not for 2 strokes. From what you have said I would look more towards the spark issue.

Ray


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## bluejets (Feb 10, 2020)

Brian Rupnow said:


> The duration on the cams in this engine are 120 degrees.


Yes but more important, what is the overlap between both cams .
Also what about condition of the condenser?


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## Brian Rupnow (Feb 11, 2020)

Here we have two new cylinder heads, which almost entail a full days work. Notice that the sparkplugs  have been moved a lot closer to the side of the head which the manifolds bolt to, which places them high above the bottom of the cylinder bore. I still have to make valves, valve guides, rocker arms and brackets but I'm happy with these. I never noticed how dirty the business end of that sparkplug was until after I had taken the picture.


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## Brian Rupnow (Feb 12, 2020)

This mornings offering to the machine Gods is four brass valve cages. These cages get Loctited and very lightly pressed into the cylinder heads. The 0.125" thru hole and the 0.25" hole are both put in in the same set-up to guarantee concentricity. The one on the left was about .002" undersize  so I knurled it lightly, which increases the diameter by about 0.010", then turned it down to the correct dimension. After the Loctite sets up (preferably overnight) I will use my George Britnel inspired valve seat cutting tool to put the 45 degree chamfer in the area where the valves seat.


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## awake (Feb 12, 2020)

Brian, what is the diameter of the bottom of the valve - .313? Also, I've noticed in some of your write ups that you machine the valve 1° more acute than the valve seat - this seems like a brilliant idea to me. I presume it lets you bed the valve in more easily?


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## Brian Rupnow (Feb 12, 2020)

Yes, the angular difference of 1 degree makes it much easier to get a good seal when lapping the valves into their cages.


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## awake (Feb 12, 2020)

Hmm, that diagram makes me realize I had it backwards - I was thinking the total included angle of the valve was less than that of the cage, rather than more. Have you tried it that way (smaller angle/more acute)? Or maybe there is a good reason not to - the slight gap might allow a bit of burning of the exposed valve seat??


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## Brian Rupnow (Feb 12, 2020)

You want the contact line at the top of the valve, not the bottom. I don't even know what would happen if you had the contact line at the bottom. Many people make the valve and seat angle the same, and there is nothing wrong with that. I just have more success doing it the way I have on the previous 18 engines.


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## Brian Rupnow (Feb 12, 2020)

I spent the afternoon making the main bases of the rocker arm support brackets. Tomorrow I will have to build a welding jig to hold all of the vertical legs of the brackets in the correct place before silver soldering the brackets together.


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## Willyb (Feb 12, 2020)

I think you are correct and it also is a place for carbon and junk to collect and possibly hold the valve open. I remember some of the early full size V8s used a slight difference between valve angle and seat.

Cheers
Willy


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## awake (Feb 13, 2020)

Thanks, Willy, that makes sense.

Brian, I apologize for side-tracking your thread. As always, you do splendid work, and what is particularly valuable to a newbie like me is the way that you walk us through your design choices. It is obvious that you've had a wee bit of experience in that area ...


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## Brian Rupnow (Feb 13, 2020)

Just had a very valvey morning. I leave the long end unturned to act as a handle while I am lapping them. Then I drill the cross holes,then I part off the handles.


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## Beamer (Feb 14, 2020)

Brian what cad software are you using


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## dsage (Feb 14, 2020)

Brian:
The quickest way to more power is more compression. Maybe it's a bit late now since you are installing valve cages but while you're making new heads take a few thou off the face of the head. You can always put a thicker head gasket in to put it back. More compression will also make some more heat and keep your plug cleaner. (of course with the requirement for a better spark).
Also, others have asked what your "real" valve timing is. I posted back in #63 on how you can measure your actual valve timing. It's a worthwhile exercise and it can also check you valve sealing and piston rings.


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## Brian Rupnow (Feb 14, 2020)

solidworks


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## Brian Rupnow (Feb 14, 2020)

So, the valves, valve cages and valve spring retainers are finished. The valves have been lapped with #320 then #400, then #600 lapping paste and have been match marked to their specific place in the heads so that I don't mix them up. I'm coming down to the exciting strokes now. I will first design and build a fixture to hold all of the parts of the rocker arm bracket in the correct relationship and silver solder it together.


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## Brian Rupnow (Feb 14, 2020)

This should make a good welding fixture to hold all of the rocker arm bracket parts in the correct relationship for silver soldering.


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## awake (Feb 14, 2020)

That should do the job! Unless ... wait: how will you affix the "arms" on that welding / soldering fixture? Will they be soldered? If so, you'll need a welding / soldering fixture to make the welding / soldering fixture. And then you may need another fixture to make that one, and ... oh, my head hurts.


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## Brian Rupnow (Feb 14, 2020)

Awake--I like making welding fixtures.  I designed welding fixtures for many years for tier 1, 2, and 3 automotive parts suppliers. Some of them were just insane, and would cost more than a new car.---Brian


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## awake (Feb 14, 2020)

Brian, I hope my comment didn't come across as any sort of critique - it was actually just a chance to indulge the warped sense of humor with which I have been cursed!


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## Brian Rupnow (Feb 14, 2020)

Awake--No offence taken. I really do like to design welding fixtures. When used in mass production of welded parts, either by a human welder or by a robot, they give truly astonishing speed and repeatability.  They don't make a lot of sense for small "one off" jobs, but sometimes there are just no other ways to align all of the parts for soldering. I spent about two hours designing and building the one I just finished, and will post pictures of it with the soldered pieces in place tomorrow.---Brian


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## LorenOtto (Feb 15, 2020)

Brian, I couldn't agree more.  As a retired aerospace tooling/manufacturing engineer with 30 years experience I can attest that a properly designed welding fixture is indispensable for accuracy and repeatability in a production environment.  In the hobby environment they help to ensure accuracy in a one-off situation.  Loren


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## awake (Feb 15, 2020)

I fully agree on the value of fixturing - that is one of the particularly helpful things to see on this forum, how to accomplish the machining of a part (or in this case, the joining of parts) that otherwise looks impossible!


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## Brian Rupnow (Feb 15, 2020)

This picture shows the finished welding fixture.  (Remember, it doesn't have to be pretty, just functional). The brass pieces which will be silver soldered together are bolted into place and are ready for soldering. If I have lived right, the fully soldered assembly will be easily removed form the welding fixture, and the pieces for the second brass rocker bracket will fit into it for soldering.


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## Brian Rupnow (Feb 15, 2020)

First soldered assembly removed form welding fixture and ready for cleanup. The fixture survived just fine, and tomorrow I will make the same soldered assembly for the second cylinder.


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## CFLBob (Feb 15, 2020)

Care to put the video camera on a tripod and start it?  I think I could watch a video of the soldering and removal.


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## Brian Rupnow (Feb 15, 2020)

Bob--If you asked a dozen people about silver soldering, you would get a dozen different answers. This is what works and doesn't work for me. I tried propane, but could never get things hot enough to work right. I use my old oxy-acetylene rig with a smaller torch tip (it came with three different size tips when I bought it 40 years ago). I clean anything to be soldered until there are no visible oxidization on the parts to be soldered. Sandpaper and wire brush for cleaning the brass or steel. I use a paste style of flux (Stay-Silv from Harris) applied directly to where I want the solder to be. I use 1/16" diameter silver solder, which comes as  roll of "wire". I direct the torch flame directly onto the brass where I want the solder to flow, and heat it to a dull glow (I have no idea what temperature that is.) I keep "dabbing" the end of the silver solder against the joint until it flows. Try not to get too much flame onto the silver solder as you do this or it will melt and run away in a puddle. As soon as the solder flows, work your way around the part being soldered. This is kind of a delicate dance like ballet---If you get it too hot, the brass will melt. If you get it too cold, the solder won't flow. Try to keep the parts being soldered away from any big pieces of metal that will act as a heat sink and suck all the heat out of the parts. (A vice for instance).---This is easier said than done. If there are places where you don't want the solder to flow, coat the area with liquid "White out" for fixing typewriter errors.  I always work from the point of view that too much solder can be filed off. Too little solder can result in a bad joint and will have to be resoldered. And that is just about everything I can tell you about silver soldering.---Brian


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## CFLBob (Feb 15, 2020)

I've done silversmithing in the past, about 15 years ago was the last time I did it.  I was actually pretty good at making jewelry without getting solder everywhere and having it stay together in a finished piece.  Silversmiths use different solders, usually called Easy, Medium and Hard (there are other grades) and sterling silver melts at fairly similar temperatures to the brasses.  Hard silver solder is the highest melting point and silversmiths often consider it a point of pride to make a piece completely with hard solder while the beginner schools teach to make the first joints with hard solder and use lower melting points for successive soldering.  If you make something completely with hard solder, anyone who has to repair it will have less issues with things re-flowing and moving.

I still have an acetylene-air torch. I need to clean it out because this is Florida and there's no telling what has made nests in or laid eggs in it, probably a Burmese python (nah - they wouldn't fit).  I need to brush up on soldering and get some of the wire solder that's used in this sort of work.  I mostly need to learn the differences in what's used and do a few practice pieces.


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## Brian Rupnow (Feb 16, 2020)

Everything fits like the 3D model says it would. Not a lot of spare room, but a miss is as good s a mile. Tomorrow I will  make up the hardened rollers which bear against the end of the valve stems, and the axles that the rocker arms pivot on.


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## awake (Feb 17, 2020)

Very nice!


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## Brian Rupnow (Feb 18, 2020)

The new cylinder heads are completely finished and assembled. Everything fits, but there isn't very much real estate left anywhere.  For those who were wondering, the compression springs are made from 0.020" wire, and are purchased.  The valves are lapped and held in place by circlips. The next move will be to remove the existing cylinder heads from the engine and install the new ones.


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## Willyb (Feb 18, 2020)

Nice work Brian. She is going to run great.

Willy


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## Brian Rupnow (Feb 18, 2020)

All of the moving components could probably have been made of aluminum. Aluminum weighs almost exactly 1/3 of what brass weighs. I was limited to brass for the bracket, because I don't have the equipment to weld or solder aluminum. Would the difference in the way the engine runs have been measurable?---Probably not, at the speed I am asking it for. The original heads were aluminum, the original rockers were steel, and the original knurled adjusters were brass. The new heads are aluminum, the new rockers are brass, and the new knurled adjusters are mild steel. The engine in it's original form ran very well, but there was always a problem on cold starts--oil would separate from the fuel and foul the sparkplugs, because they were right at the very bottom of the cylinder. I'm not reinventing the wheel with these new heads, All I'm doing is correcting what I determined was a design flaw. I haven't dismantled anything from the old heads, the design flaw only appeared when the cylinders were horizontal. The old heads may get re-used on a new engine with multiple vertical cylinders.


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## Brian Rupnow (Feb 20, 2020)

People have been asking about the relative size the engine is that I am working on. Canadians don't use pennies anymore, so the only closest thing I could find for a visual comparison is a matchbook. In this picture, I have my adapter screwed into the sparkplug hole and 50 psi on the air hose. No leaks at the exhaust pipe nor the carb air intake. Having established that cylinder as being okay, I will now move over to the other cylinder and perform some magic over there.


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## Brian Rupnow (Feb 20, 2020)

I had an interesting day today. I went to a heavier valve spring of .038" wire diameter. These are beefy little buggers. Too strong to compress with my thumbs and slide the locking collar into place. I had to figure out how to make a spring compressor. Honestly, I have never used any springs that are over 0.020" diameter on any of my engines. The "lift" on the cams for this engine is just a bit more than 1/16". The coin is a Canadian $2, called a "Twoney"--that name was derived form the 1$ coin issued a few years ago that had a loon on one side, so of course it immediately got named a Looney!!!


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## awake (Feb 20, 2020)

Brian, why such a heavy spring? I'm also curious about the gasket that I think I see between the head and the muffler. What do you typically use for gasket material?


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## Brian Rupnow (Feb 20, 2020)

Combustion chamber hasn't changed at all, other than the location of the valves and sparkplug. Biggest change of all was the shape of the rocker arms. They went from simple "straight' pieces of steel with rollers on the center to the new ones with the cantilevered rollers at the end. In test mode, with the adapter screwed into the sparkplug hole, the cylinders sealed up tight up to 50 psi. of air pressure No leakage of air out the exhaust pipe nor out of the carburetor throat, nor past the rings. The valves sealed great under "test" conditions, but engine had no (or very little) compression when cranked over. Nothing gets past the Viton o-rings, no leaky head gasket. Conclusion is that the valves aren't seating properly. They are lapped, and do seal under "test" conditions but not in normal "start the engine" mode. Normally, if I can get an engine to fire at all, the force from igniting fuel will force the steel valves against the brass seats hard enough to make a perfect seal. Tried to start it already, and there simply wasn't enough compression for the fuel to ignite. It's rather coincidental that Boomer has been talking about valve springs.--That is where I ended up going anyways as that's about the only thing left to try. Ignition and valve timing hasn't changed since the last time I had the engine running. I can push the valve off the seat, against the new spring pressure when gripping the head between my thumb and finger. It is noticeably harder to do that now, but my cams, lifters, and rollers on the rocker arms are all heat treated 01 steel. I did have to make a spring compressor, because it is very finicky work trying to get the spring compressed, the keeper in the right spot, and the c-clip on without something to compress the spring and let me work with both hands.  The push-rods are 1/8" diameter about halfway up their length, then are reduced to 1/16". I will probably make new pushrods tomorrow that are 1/8" diameter over the full length. I use .031" thick waterpump gasket for my head gaskets. I have never had a head gasket burn or "blow out".


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## dsage (Feb 21, 2020)

SO - what is your valve timing? Especially at BDC where intake closes and Compression starts?


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## Brian Rupnow (Feb 21, 2020)

I found exactly what I had set it for. Both exhaust and intake lead by about 20 degrees.


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## Brian Rupnow (Feb 21, 2020)

I haven't installed the head with new springs yet. I'm ready to go, but I want to mount a 0.060" spacer under the rocker arm bracket but wife isn't up yet. This has become my morning routine. Wake up, get dressed, make a coffee, then head down to my computer and look at the forums to see what everybody else has done.---Quietly. My bandsaw is out in my main garage right under her bedroom. I am going to saw the spacer out of 1/16" plate, and the bandsaw makes a Hell of a racket. I'm putting the spacer under the bracket to raise it up 1/16" because as you can see in the picture, clearance between the adjusting bolt in the end of the rocker which adjusts the valve lash is uncomfortably close to the head of the bolts which hold the intake and exhaust flanges in place.


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## awake (Feb 21, 2020)

Brian Rupnow said:


> Combustion chamber hasn't changed at all, other than the location of the valves and sparkplug. Biggest change of all was the shape of the rocker arms. They went from simple "straight' pieces of steel with rollers on the center to the new ones with the cantilevered rollers at the end. In test mode, with the adapter screwed into the sparkplug hole, the cylinders sealed up tight up to 50 psi. of air pressure No leakage of air out the exhaust pipe nor out of the carburetor throat, nor past the rings. The valves sealed great under "test" conditions, but engine had no (or very little) compression when cranked over. Nothing gets past the Viton o-rings, no leaky head gasket. Conclusion is that the valves aren't seating properly. They are lapped, and do seal under "test" conditions but not in normal "start the engine" mode. Normally, if I can get an engine to fire at all, the force from igniting fuel will force the steel valves against the brass seats hard enough to make a perfect seal. Tried to start it already, and there simply wasn't enough compression for the fuel to ignite. It's rather coincidental that Boomer has been talking about valve springs.--That is where I ended up going anyways as that's about the only thing left to try. Ignition and valve timing hasn't changed since the last time I had the engine running. I can push the valve off the seat, against the new spring pressure when gripping the head between my thumb and finger. It is noticeably harder to do that now, but my cams, lifters, and rollers on the rocker arms are all heat treated 01 steel. I did have to make a spring compressor, because it is very finicky work trying to get the spring compressed, the keeper in the right spot, and the c-clip on without something to compress the spring and let me work with both hands.  The push-rods are 1/8" diameter about halfway up their length, then are reduced to 1/16". I will probably make new pushrods tomorrow that are 1/8" diameter over the full length. I use .031" thick waterpump gasket for my head gaskets. I have never had a head gasket burn or "blow out".



Thanks for the explanation. So, if I understand correctly, you are using the stronger springs to help force the valves closed in order to get compression. Question: once you have run-in the engine, fully seating the valves, would there be any advantage to going back to softer springs? I don't know enough to know what the impact is, but wondered if the heavy springs would leach some power from the engine - ??


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## Brian Rupnow (Feb 21, 2020)

Awake--I have completely reassembled the one cylinder with the heavy duty springs on the valves. If I see an improvement, I will do the other side to match. Will it hurt the performance of the engine? Probably, as it takes more power to lift the valve off it's seat. I don't really know. I've never used springs this heavy before. I have about fifteen i.c. engines that I have built, and none of them have springs heavier than 0.020" wire diameter. I am in "Try it and see what happens" mode.


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## awake (Feb 21, 2020)

I await the results with interest! I just made the springs for the modified Webster that I'm working on; the plans call for the intake spring to be .013" wire and the exhaust spring to be .022" wire. The former is _really_ light - I've wondered if it will be too light, but we shall see. I'm almost to the point of assembling the valve cage, attaching to the head, and seeing what sort of compression I have ... or not!


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## dsage (Feb 21, 2020)

Brian Rupnow said:


> I found exactly what I had set it for. Both exhaust and intake lead by about 20 degrees.


I was thinking more in terms of when the intake closes. That would be part of the cam lobe duration.
If the intake is late closing it will be robbing some compression. Also late close will result in some charge being pushed back out the intake. 
Large overlaps (and duration) are really racing engine type configurations  where the rpm and mass of the moving air figure into things. You're better off with next to no overlap (maybe 5 deg at most) at TDC and get the intake closed at or very near BDC.
More like the "gas saver" cams commonly available for vehicles.


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## Brian Rupnow (Feb 21, 2020)

The 0.013" spring is just about perfect for an atmospheric valve which doesn't use a cam.  The 0.020" or 0.022" is absolutely right for the exhaust valve which is operated by a cam.  I have about 16 i.c. engines I have built with those size springs and they worked fine.


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## awake (Feb 22, 2020)

So, you're saying it is going to run on the first try, right?


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## Brian Rupnow (Feb 22, 2020)

Awake--The most critical thing with these small i.c. engines is that the valves seal completely. If you get the valves and seats right, then your engine is almost guaranteed to run.  Might not run good---might not run continuously, but it will run. If the valves leak, and you don't get good compression, then you will just make yourself crazy trying to figure out what is wrong. These small valve springs work great, but they depend on a very smooth and frictionless interface between the valve guide and valve stem, and a perfect lapped seal between the valve face and the valve seat. Using a steel valve and a brass seat, even if its not a perfect seal, if you can get the engine to fire at all while you are trying to start it, the pressure from the exploding fuel will drive the valve face against the brass seat hard enough to make the brass seat conform to the shape of the valve. That is why many of these small engines run better and better for the first half hour of running. If you absolutely can't get the valves to seal, you can resort to other things like much heavier stiffer valve springs (such as I just did on the twin cylinder I'm working on), but I don't recommend it.


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## awake (Feb 22, 2020)

Thanks, Brian. Soon, soon I will be at the point of testing compression ... meanwhile, let me not further derail your thread. Did the stronger springs produce the desired result?


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## Brian Rupnow (Feb 23, 2020)

There is no joy in Mudville---I have no good news to report. The engine is reassembled with my new cylinder heads (the uber strong valve springs are only on one of the cylinders). With my adapter screwed into the sparkplug holes, the cylinders both hold 60 psi air pressure, with no air escaping past the valves.  I have tried to start the engine and it isn't happening. I even went so far as to set it up on my bench and drive it for half an hour to see if that would seat the valves a bit better but it didn't seem to do anything.  I am going to go out today and buy a socket and pigtail for a 12 volt bulb and wire it up through the points so I can get a really good concept of the ignition timing. I will also do one more check of the valve timing. This time I will check valve timing on both cylinders. The cams are made as four individual components and Loctited to the camshaft. I doubt very much that they have spun on the camshaft, but I will check it. I know a thousand things to check for on engines that won't run, and I've used up 998 of them. If this engine doesn't run after a final ignition and valve timing session, it's going up on the shelf. I have an idea for a new and different engine in my head that I would like to spend some cad time on, and I'm ready to move on.---Brian


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## CFLBob (Feb 23, 2020)

If you put it aside, don't stop thinking about it.  Taking a break to think about something else is often a good way to get the creative thoughts flowing again.   At least, it always has been for me.


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## George Punter (Feb 24, 2020)

Good Day Brian,
I have been following your engine construction and it brought back many memories of the first engine that I designed and made ( also a flat twin of 20cc). Like you I encountered problems but gradually eliminated them one by one. It’s all part of that learning curve. On some of my engines I use bronze for the inlet seat/ guide and cast iron for the exhaust and leave the all the seats (valves included) as machined and do not use ant lapping paste. As your engine has good compression there are a couple of points that you could check - is the spark on the compression stroke and you could also try more advance. I am sure your engine will burst into life soon. One time I was working on a Velocette LE 200cc that would not go only to find out that the chap had the plug leads on the wrong cylinders!  Keep up the good work.
George.


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## Brian Rupnow (Feb 24, 2020)

Okay--An update. this afternoon I checked and reset the ignition timing. I even wired in a 12 volt light thru the ignition points so I could see exactly when the points opened the circuit. Stuck  a hex wrench down the sparkplug hole and turned the engine over by hand, one hand hanging onto the hex wrench which was in contact with the top of the piston and the other hand slowly turning the vaned flywheel. I didn't really like the ignition timing it was set at, so I changed the timing a bit until I was happy with it. Then I slowly turned the engine over by hand , still hanging onto the hex wrench, and got a good reading of when the intake and exhaust valves began to open. That was right, so I then moved over to the other cylinder and repeated the act. Valve timing was good on that cylinder too. So---the cams haven't slipped on the camshaft. Tried to start the engine, and it didn't start, however the right hand cylinder was puffing smoke and getting warm. The left hand cylinder was too (that's the side with the heavy valve springs) but not as much as the right cylinder. I put new fuel in the tank, although I don't really think that Naptha goes bad with age. Tomorrow I'm going to set the engine up on the bench and drive it with the electric motor, until it flies or dies. I'm not going to work on this anymore. Now, an observation::--This is fairly important. The crankshaft has bronze bushings on it, not ball bearings. There is some runout on the crankshaft, but not much. The thing is, and you'll have to believe me on this---If there is any runout AT ALL on a crankshaft, it's going to squirm as it rotates in the bushings which support it. Consequently, the bushings will be worn away on a taper on both sides of the bushing centerline. Then it is only supporting the revolving crankshaft on a thin "line of contact" in the center of the bushing, which quickly wears away. The result of this is sloppy fit between the crankshaft and bushings. This won't prevent an engine from starting, but it will clunk and clank while running, and if your ignition cam is supported on the crankshaft, the points gap will not be stable. HOWEVER---And I wouldn't have believed it if I hadn't seen it---A single race ball bearing will tolerate a small amount of squirm without damage to the bearing or the  shaft. I have found this out by my own personal experience, and will never again build an engine with bushings supporting the crankshaft. Again, on a 4 cycle engine this will not keep the engine from running.  It will screw up a 2 cycle engine because a squirming crankshaft will quickly wear out the crankshaft seals and the crankcase will no longer be "air tight". That's it folks. I'm done with this. If the engine does decide to run tomorrow, I will shout "hurray" and post a video of it, and tell you all how clever I am. If it doesn't, it will go up on the shelf and stay there.---Brian


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