Yet Another Webster Begins
- Thread starter CFLBob
- Start date
Help Support Home Model Engine Machinist Forum:
Looking at your attempt to start by hand there appears to be no or very little compression from the video and on your attempt to start with the drill it is obvious that the compression is low. take the plug out and put your finger over the hole and check compression. if low check the exhaust valve for leaks does it have clearance from the tappet rod when on the back of the cam
No, I think you're right and that's my big concern. When I first put this together, it was much harder to crank that flywheel by hand. I ran it with my electric drill driving the motor for 45 minutes or an hour and it got very loose. That's what I'm trying to investigate right now.
My Duclos flame eater makes a very noticeable snorting sound when I turn the flywheel. This one makes less noise, but yours seems like it bounces back from the compressed air. I think mine should be doing that. I want to try some of the tests people have suggested and see if I can tell more about the compression.
It sparks very well with the plug out of the cylinder and picking up ground from the base plate.
I'm going after the compression questions today.
CFLBob
With every engine I've done, If the compression is good then the other adjustments don't seem that difficult
I usually test compression like this: when I pull the piston back to the BDC , when I release the flywheel ( without cylinder head , I sealed the cylinder by hand )
1 / With piston and clean cylinder: piston will go up TDC about 1/2.
2 / piston and cylinder with a little oil w40: piston will go to TDC, or at least near TDC
That compression is good enough with me. ( If the valve is airtight )
Springs of atmospheric valve :
With every engine I've done, If the compression is good then the other adjustments don't seem that difficult
I usually test compression like this: when I pull the piston back to the BDC , when I release the flywheel ( without cylinder head , I sealed the cylinder by hand )
1 / With piston and clean cylinder: piston will go up TDC about 1/2.
2 / piston and cylinder with a little oil w40: piston will go to TDC, or at least near TDC
That compression is good enough with me. ( If the valve is airtight )
Springs of atmospheric valve :
Last edited:
If everything is right, then when you are turning the engine with your drill, you will definitely feel the engine "kick" when it fires. I know that when you are actually turning the motor over there is a lot happening and a lot of noise. You will however feel the kick. My best bet is that your valves aren't sealing properly.---I had a terrible problem with that when I built my Webster. even if the valves are leaking a bit, as soon as the engine starts to run, the valves will seat themselves under pressure and provide an air tight seal.
- Joined
- Sep 2, 2011
- Messages
- 1,381
- Reaction score
- 370
on my Webster, I do not feel the kick with the drill and rubber disk, but I just take it off and it keeps going. on the valve blocks, mine seeps just a very minute amount between them, still runs. I surface plate sanded each surface and did not use a gasket. on the head to cylinder I used red high temp silicone to seal it. I know silicone and gas do not mix but it worked. (I don't think I needed it but have not pulled the head to remove the silicone since I got it running).
if you put your finger of the carb air intake and rotate the engine by hand, will it suck enough gas into the engine to flood it? if so id say you are good on suction and intake spring. if not then spring or valve timing is likely issue. I believe my engine would run even without the rings.
if you put your finger of the carb air intake and rotate the engine by hand, will it suck enough gas into the engine to flood it? if so id say you are good on suction and intake spring. if not then spring or valve timing is likely issue. I believe my engine would run even without the rings.
Let's get back to your ex. valve timing. Looking at your video Bob, I see at 4,8 and 17 seconds the ex. valve just closed and the con rod looks high on the crank web, too many degrees after TDC. You have very little draw left on the in. valve and that's why nobody sees it moving and also unnoticeable compression. Wrong valve timing explains these symptoms so a possibility in your Webster. Is your ex. valve closing at or near TDC ? If it is then the cam timing is fine and my breakdown of the video by the second wasn't enough for these conclusions.
Last edited:
- Joined
- Sep 2, 2011
- Messages
- 1,381
- Reaction score
- 370
could it be that valve timing vs ignition timing was done with one timing done looking with the engine turning in one direction and the other timing was done with the engine rotating in the other direction. sort of like doing valve timing by looking at the wrong side of the engine or ignition done when looking at the wrong side of the engine?
maybe these photos will help - I'm back in my office today so can take them.
crank position when the points cam has allowed the points to make full contact - photo of the crank side as well as the points cam side to show what position the crank should be in when the points make full contact
maybe these photos will help - I'm back in my office today so can take them.
crank position when the points cam has allowed the points to make full contact - photo of the crank side as well as the points cam side to show what position the crank should be in when the points make full contact
Attachments
I was just going to go play with trying to find leaks, but this has gotten important.
Werowance - these pictures are very valuable. Here's mine when the points should fire. Well, within "a couple of" degrees of firing. (Note my picture is tilted - look at the bench in the background. ) I think it looks quite a lot like yours.
and the points
That looks a little early, but close.
The Exhaust Cam setting instructions on the last page say to set it 15 degrees before Bottom Dead Center and that's what that little CAD drawing I put up showed. This is the engine.
Werowance - these pictures are very valuable. Here's mine when the points should fire. Well, within "a couple of" degrees of firing. (Note my picture is tilted - look at the bench in the background. ) I think it looks quite a lot like yours.
and the points
That looks a little early, but close.
The Exhaust Cam setting instructions on the last page say to set it 15 degrees before Bottom Dead Center and that's what that little CAD drawing I put up showed. This is the engine.
That seems reasonable...as long as your bottom pic shows the exhaust cam just starting to open AND that this pic is taken at the END of the POWER stroke (in other words, about a half of a turn of the flywheel after ignition TDC. That part is important.).
IF that is the case, I would pull your valve block off and check the compression by holding your finger over the hole in the side of the engine frame.
IF that is the case, I would pull your valve block off and check the compression by holding your finger over the hole in the side of the engine frame.
Last edited:
That picture is supposed to match this one from the plans:
15 degrees before bottom dead center the stem of the exhaust valve just starts to lift.
When I do that I get good compression. It makes a good squeaking sound as the air pushes my thumb out of the way and noticeably quite a bit harder to move the flywheel. So it's my valve assembly that's leaking.
You are now entering the "Twilight Zone".---Leaking valves----This is the part that separates the men from the boys Bob. I almost suffered from a Conniption fit with my first two i.c. engines, the Webster and the Kerzel Hit and miss engine because of leaking valves.
Does it matter that I get a squeak on the compression stroke, bottom to top dead center, but not when piston is going from top to bottom?
But I have your distilled wisdom that I worked by - posted here a few years ago. So my first guess will be to lap them against the valve guides again, after some disassembly. Before I start over and make the entire assembly over - valve guides, valves, and the three aluminum pieces.
Nah, the squeak is caused by compressed air escaping around your thumb. When the piston is going the other way it sucks your thumb into the hole, plugs it, and pulls air in around the leaks.
- Joined
- Sep 2, 2011
- Messages
- 1,381
- Reaction score
- 370
probably not the case, but your points cam - the flat doesnt seem as cut down as much as mine? and my points which my pic doesnt represent it but mine seem to be touching more flatly or symetricly or some other way of saying the contacts are flatly and fully engaged and the cam isnt influincing them in the least when its on the flat. that said i probably cut the flat further than i should have.
i have another question and im sure it was already addressed by others in this thread, but im going to ask anyway. i have no experience with the electronic ignition box you are using (ive only dealt with pertronix on tractors). does it still require a condensor or capacitor? or is it built into the kit?
i have another question and im sure it was already addressed by others in this thread, but im going to ask anyway. i have no experience with the electronic ignition box you are using (ive only dealt with pertronix on tractors). does it still require a condensor or capacitor? or is it built into the kit?
- Joined
- Sep 2, 2011
- Messages
- 1,381
- Reaction score
- 370
bob, it also just occured to me, i have a webex account at work and a web cam that i can bring home on the weekend or after work. if it would help i can do a webex and let you study my engine and move it arround and zoom in on anything you want to see. or at least as much as the rinky dink web cam can do. if you are intersted let me know and ill try to bring all that home tommorow. including the engine.
The capacitor is built into the kit. You can use points or a hall sensor and even a switch. I think I went with points because it was cheaper and seemed easier.
Roy Scholl who runs the company is closing down options to retire, and they might go away. They included a little slip of paper that they're looking for someone to buy the business. Roy's CDI Ignition Systems
I think my points (from NAPA) are defective. They work for a while and then it's like there's no spring in there. They won't snap closed. I've never seen, never even heard of such a thing. It was a PITA to get them, this is the second set I bought, and I'm pretty annoyed with them.
Thanks for the great offer. I feel like it's probably not completely desperate yet. Maybe I'm too optimistic but I'm going to go after the problem with valves not sealing. Hopefully I won't have to remake the top and bottom pieces and just spinning them with some abrasive will seat them better and fix things.
Of course I may have a different opinion in a few more days.
- Joined
- Sep 2, 2011
- Messages
- 1,381
- Reaction score
- 370
Roy helped me with some ignition parts and also included the retirement slip. i envy anyone who can retire happily and look forward to when i can as well. just wish i could do it sooner than later. he was very nice to help me with caps and points contact tips etc
now next i will say that i appolgize for blowing up your build with so many replies but it just occured to me that points normmaly fire the coil when they disengage and break the flow of current (counter intuitive if you dont understand it - which is me most of the time) so since points normally are timed to disengage to fire and i think that pertronix (i may be wrong) fire when "engaged" then could the points cam be 180 out on the electronic igintion? i bet Roy could answer it in a heart beat.
ill try to stop bugging you with all the suggestions. im just as anxious as i bet you are to see it run is all.
now next i will say that i appolgize for blowing up your build with so many replies but it just occured to me that points normmaly fire the coil when they disengage and break the flow of current (counter intuitive if you dont understand it - which is me most of the time) so since points normally are timed to disengage to fire and i think that pertronix (i may be wrong) fire when "engaged" then could the points cam be 180 out on the electronic igintion? i bet Roy could answer it in a heart beat.
ill try to stop bugging you with all the suggestions. im just as anxious as i bet you are to see it run is all.
