Building a Bonzer Bonzer

[Philjoe5]

Here's where I'm at with this engine. Using the starter designed by Brian, which works great BTW, the engine seems to fire at times and then doesn't fire at all when I squirt fuel into the intake manifold.

I connected up my version of a Jan Ridder's vapor carb . I've tried the air bleed adjustment lean and rich but no go, usually not even a pop. I know I'm sucking air through it because through evaporation the tank gets very cold. I checked the spark and it's yellow and fires consistently. I've tried 20 degrees to 5 degrees before TDC for the spark. Exhaust valve lift starts around 10 degrees before BDC. I've varied that up to 0 degrees before BDC.

The intake valve sucks open and closed when I spin the engine. Thinking maybe I didn't have a good cylinder head seal, I remade the gasket for that this evening and will give it a try tomorrow.

Did I overlook anything?

Cheers,
Phil

 

[Generatorgus]

Congrats Phil, You have entered into the Twilight Zone of IC engine building.:hDe:
It can be a very humbling experience.
You spend months making parts and are encouraged by the successes in your machining. You get all parts assembled, then :fan:the frustration starts.

It took me building a second engine to learn how to get my first engine running, well over a year. Right now I've got two good runners and a third in the ZONE. And for some reason I started building a fourth.

I don't know if I have enough experience to give advice, but go back and check everything, valve timing, ignition timing and be especially critical of compression, which I think is the most important aspect.
A light flip of the flywheel should cause bounce back, I like it when it rebounds several times. That is a good indicator.
Leaks at the valve stems can cause problems, put some oil on the stem and see if that helps or changes anything. Check the spark plug, see if it's wet from flooding.

My experience with vapor carbs is very limited, but I'm thinking that just because their is fuel in the tank it may have lost it's volatility. Try fresh fuel or even switch to a different type.
Also vapor carbs do nothing to lubricate the cylinder, and that can cause loss of compression.
Another thing, do you have the same springs on the valves, listen or watch to see if the exhaust valve is inhaling, it should have a heavier spring, and maybe you could try a lighter spring on the intake.

I'm sure you've tried all of the above, you seem to be very thorough, but keep a stiff upper lip, you'll get it sooner or later, hopefully in time for Kinzers.

GUS

 

[Brian Rupnow]

Send me your real address and I will send you a brand new carb that I guarantee will work on your engine. It's an extra one I built while playing with the Rupnow engine last summer. I can send it out today. I don't really trust the Jan Ridders carb that much,=.---Brian

 

[Lawijt]

With the Jan Ridders vapor carb you can never flood the engine. They are working very good. Also you can put 1-2% 2-stroke oil in.

Barry

 

[Brian Rupnow]

Lawjit---the 1 to 2% oil never vaporizes.--It just stays in the tank and starves the cylinders for lubrication.

 

[Philjoe5]

Thanks for the inputs guys,

Gus: I remember you were struggling with the Wyvern about a year ago. I assume you got it running then?

listen or watch to see if the exhaust valve is inhaling

What does that mean? It should be exhaling right?

Brian:

I will send you a brand new carb

That's a very generous offer. I'll give this carby a bit of time and when I hit the wall I'll send you a PM.

Barry:
I haven't given up yet

When I started this engine around August 1, 2013 I told myself if I had a runner in a year I'd be a very lucky guy. I know building an IC engine is very much like making a pair of gears..you can't have good results in the first 99 machining steps then miss 1 step and have anything useful.

Thanks again for the advice and assistance. It's much appreciated

Cheers,
Phil

 

[Philjoe5]

I'm getting a few more pops today but still no joy.

I do have a few questions though.

Does the spark occur just as the points open, or when the full gap is reached? It's hard to tell by observing the spark plug outside the engine.

If the intake valve is sucked open consistently, does that mean the seal in the cylinder is good. It's hard to feel compression because the engine is still tight, but is definitely loosening up. I'm inclined to look at compression because I think I have the timing set about right.

Cheers,
Phil

 

[Brian Rupnow]

Spark occurs as the points open, causing the primary field to collapse in the coil. If the intake valve is sucked open, that means that your exhaust valve is sealing properly and that probably your rings are good. However, if the engine is so tight that you can't be sure about whether or not you have compression, then something is wrong. You should most definitely be able to feel the compression. How stiff is the engine to turn over with the sparkplug removed? It should be a very noticeable difference. If there is not a very noticeable difference, then either you don't have good compression or your bearings are unusually stiff. As a first suggestion, put a v-pulley on your engine, take out the sparkplug, oil everything to excess, and drive it with an electric motor for a couple of hours to loosen it up. Then when the engine has loosened up considerably, put the sparkplug in, make sure the ignition and fuel supply is okay, and drive it with the electric motor, making sure the motor is turning it the correct way. If it starts to pop at all, that means it is firing, and the fact that it is firing will help to seal any small leaks in the valves. If the electric motor driving it is a standard 1750 RPM motor, try for a 3:1 reduction between v-belt sheaves so your engine is rotating at about 600 rpm. The intense pressures created by combustion when the engine fires seems to help seat the valves and seal them much better than you can accomplish by hand grinding and lapping them. The most likely cause of an engine not starting is non sealing valves. It has always been my prime bugaboo with i.c. engines. You may have too light a spring on your intake valve. That lets vacuum open the valve easily, but the spring may be too weak to close the valve completely when the compression cycle begins. On all of my engines, the intake valve moves very slightly--in fact, when cranking the engine to start it, sometimes you can't even see it move. When the engine is running, the valve appears to vibrate, more-so than actually opening an appreciable amount. If all else fails, take the head off and re-lap the valves with first 400 grit lapping paste, then with 600 grit. If you have a finger chuck to grip the stem of the valve, hold the finger chuck with--what else---your fingers--and pull the valve up against the seat as you rotate the chuck back and forth between your fingers 10 or 15 times. then turn the finger chuck 45 degrees and repeat--do this about 4 times with first 400 grit, then with 600 grit. That is the best way to go. Do not, on any account try to power lap the valves, for on an engine this small it will just burn the valve and seat faces and destroy them.

 

[Philjoe5]

Thanks Brian, you've given me a lot to chew on

Cheers,
Phil

 

[Generatorgus]

Phil,
The exhaust valve can suck air just the same as the intake, it needs a little heavier spring to keep it closed so that the intake does all of the inhaling.

The Wyvern: it runs, but not at all like I want, but it will sooner or later, I just have to mess with it more, I tend to get sidetracked a lot. It's throttle governed and the carb seems to may be the problem, but I'm also having problems timing it, right now I'm blaming the Hall sensor.

On the subject of tightness, isolate the problem. Is it in the cylinder or the crankshaft. Unfasten the conn rod, see if the flywheels spin freely with no tight spots.
If they don't it may be the bearings are tight or misaligned. I don't recall if you used split main bearings, I see bearing caps, but if you did just try loosening the caps, you may need to shim a little clearance.
The only resistance to turning should be from the spring on the exhaust valve when it starts to lift, and that should not be that much.

It may be tight in the cylinder or binding on the conn rod. The conn rod can bind against the crank if there's any misalignment.

Possibly the ring fit is tight.
I totally gave up trying to make iron rings, too dicey for me. After several tries in he H Ford and the Lil Bro I gave them up, and went to O-rings.

A guy at CF told me how to make the fit (his Lil Bro was running perfect while mine was just sitting on a table).
I made a new piston with two groves just in case, but only made one O-ring and tried it. It fired immediately and settled into hit and miss.
After that epiphany, I did the same procedure on the H Ford and it also emerged as a good runner.
Myself, I'll leave iron rings to the more skilled or more patient. Iron or O-ring there should be very little resistance, except the resistance of compression. In my case the iron rings were the cause of poor compression.

Overall, with my skill combined with the accuracy of my machinery, I'll accept a little loose over a little tight any day.

 

[Brian Rupnow]

Phil--I have read thru your post again, and I see that you made your own cast iron rings. I, like generator Gus have never had good luck with cast iron rings. I have gone directly to Viton O-rings on my engines and never had problems. If you do use a Viton ring, use a ring of 1/16" cross section with an o.d. equal to the bore of your cylinder. Make the ring groove 0.060" deep x 0.93" wide. A 1/16" cross section o-ring actually measures 0.070" cross section. If you want to stay with the iron rings, then like my original post says, soak everything with oil and drive it with an electric motor for 2 to 4 hours to "seat" the rings so they will seal better.

 

[Philjoe5]

Gus, Brian,
Thanks for the advice and encouragement.

I've got lots to investigate. I managed to vaporize all the fuel (Coleman white gas) in my tank with all the starting attempts. So that tells me I am pulling air well enough. I've got spark, and I think the timing is OK. I found a major source of binding and that was the attachment of the engine to the baseplate. I had put the engine frame a bit out of alignment so I fixed that. I also found the drip oiler to the cylinder was blocked by a flake of brass so I opened that up and now it gulps 30 wt oil.

With all that said, a few tries were made with some joy. At one point the engine was firing at a speed almost faster than the electric drill speed. It fired long enough to make the head and cylinder quite warm, but not hot. I’m fairly sure I now have maybe a minor timing issue to address OR the carby isn’t up to it. I may PM you soon on the carby offer Brian.


There's no doubt that getting oil in the cylinder, and loosening up the engine has helped a lot.


I’d be a basket case without the benefit of my electric starter – thanks again Brian for the plans.

I will try not to wear you guys out. You’ve given me loads of ideas to work with so I’ll keep at it.

Brian, I seem to recall when you had made all the air/steam engine designs you wanted you said, time to try an IC engine. That’s where I’m at now. I’ve got all the steam engines I want so this is the last frontier. I’ll remake any or all parts I need to for a runner. May take time but I have the luxury of good health, time and motivation to keep at it.

On top of all that, the engine designer from Australia is coming to visit for the Cabin Fever show. I can pick his brain over a few rum and cokes!


Right now I'm waiting for my drill batteries to recharge before I have at it again.


Cheers,
Phil

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[Brian Rupnow]

Try more spark advance. Take the sparkplug out and heat the end of it and quickly put it back in and try it. If you had a carb I would say close the needle valve all the way and then open it very slowly as the engine is turning over. Squirt some oil around the stems of the valves. Use real gasoline instead of Naptha--its a bit more volatile.-Pray.--Put on clean socks!! That almost exhausts the things you can do to start one of these things for the first time.---I can ship the carb out tomorrow.---One more thing I just thought of--My battery powered drill doesn't really turn the engine over fast enough. It makes a hugh difference to turn the engine over with my 110 volt electric variable speed drill at a much faster clip.

 

[Philjoe5]

It makes a hugh difference to turn the engine over with my 110 volt electric variable speed drill at a much faster clip.

You're right about that. When my battery is low and spins the engine slowly it doesn't want to fire.

PM being sent

Cheers,
Phil

 

[Brian Rupnow]

Phil--I will be sending this out to you tomorrow.---Brian

 

[Brian Rupnow]

Okay Phil--the carb is on its way. I just slipped up to the post office now and sent it by air express. The post office guaranteed delivery within 5 business days as long as U.S. customs doesn't get involved in it. I will send you a private message with your tracking number in it.---Now we can both set around and play the "Waiting for parts" game.--Actually this should work out well. Designed by an Australian, built by a Yank, with a couple of Canadian parts.----a truly international effort!!!---Brian

 

[Fluffy]

G'Day Phil,
Just read your posts on your troubles starting the Bonza.
This may possibly help.
I set the timing on my Bonza by finding the TBC with a dial indicator down through the plug hole. When on TDC, I adjusted the point gap so that I could just pull a cigarette paper through the gap.
I used 98 octane petrol & primed the carburettor by putting my thumb over the venturi & turned the engine by hand until fuel entered the carby. Then completely closed the needle & then backed it off approx. 1/8th of a turn. I used a pull rope to turn the engine & as the engine was rotating after pulling the starter rope I choked the venturi with my thumb to close off approx. half the venturi intake diameter. On the second attempt the engine fired a couple of times & stopped. I then backed off the needle a "bees ****" more & tried again still choking the venturi & the engine started & ran continuously.
I made a number of venturis & found that the engine started & ran the best when the venturi drilled with a No.17 drill was installed.
Regards,
Don.

 

[Philjoe5]

Thanks for that Don. I've been adjusting the points so they just start to open at about 10 degrees before TDC. It seems you have the points just opening at TDC. I'll give that a try.

I did have one part move on my latest starting effort. The bracket holding the rocker arm rotated just enough to shift off of the valve stem. I adjusted that to where it should be, then put a drop of red threadlocker on it. I'd have used the green stuff but I was out of stock.

One by one the weak links in the build show up and need addressing.

Cheers,
Phil

 

[Philjoe5]

After a bit of fiddling with absolutely no response from the engine I made a sad discovery. When the rocker arm bracket shifted the rocker arm contacted the intake valve bending the stem. I did make spare valves and cages but this puts a wrench in the works as they say.

Tomorrow, damage control

Cheers,
Phil

 

[Philjoe5]

Damage isn't too bad. Seems like all I've lost is the intake valve and I have one or two spares. The seat looks OK on the intake cage which is good because that's in the head with red Loctite.

The problem I need to deal with is the rocker arm bracket. It's 2 pieces held by a #6 flat head screw. There shouldn't be a lot of stress on it so I don't know why it would break loose and swivel over to hit the intake valve. It would be easy enough to make a 1 piece bracket and I may do that. My silver soldering skills are 1 notch below my Loctiting skills, so I'd rather not practice on this part. There's very little contact area between the 2 parts.

The downer, of course, is to actually hear the engine fire for 10 - 20 seconds yesterday, and then :fan:. But that's what it's all about.

Besides I've gotten some good advice from some members here and the offer of a carby from Brian.

My new hobby has just changed from engine builder to engine repairman

Cheers,
Phil