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I decided I should continue this thread here since this seems to be have become another work in progress.
I got the new flywheels remounted and changed over to a carburetor that I had originally built for the engine. The carb is pretty basic, but it was readily available. The engine ran a little better, but still mostly on one cylinder. And, I couldn't get it to idle very slow.
So, I abandoned the carburetor and decided to go back to a vapor carb. I happened to have a glass jar that was 2 - 3 times taller than the pimento jar I had been using. And, it turns out, the pimento lid was the same screw size as the new bottle, so I just switched bottoms. This eliminated the splashing up into the intake tube and the engine smoothed out and ran pretty well, again, on one cylinder with the other cylinder firing intermittently. I increased the rocker arm clearance on both intake valves by quite a bit and this allowed me to slow the engine down to a pretty reasonable idle. The good cylinder was now firing ever time and the missing cylinder still fired intermittently. I removed the push rod from the intake valve on the good cylinder to see if I could get the engine to run on the missing cylinder. My thought was that maybe it wanted a leaner (or richer) mixture or maybe the other cylinder firing was interfering with the bad cylinder. However, I could barely get it to run on just the bad cylinder. I put it all back together and fired it up again. This time, I discovered when opened up the throttle a little, then I put a load on the engine by holding a rag against the flywheel, I could get it to fire on both cylinders pretty consistently at a pretty slow speed. I don't get it! But if all I have to do is put a load on the engine to make it run the way I want, so be it.
So here is what I've checked so far. Compression on both cylinders is excellent. Both intake valves are opening and closing at about the same position. Same with the exhaust valves. Ignition timing is identical for both cylinders. I'm beginning to think I might have a small air leak in the intake side of the bad cylinder. This is making run real lean and only firing ocassionally. Could be the manifold or it might be the valve stem on the intake valve. I might try putting a couple of drops of heavy gear oil on the valve stem and see if that seals it up temporarily. The other thing I haven't checked is the gap on the spark plugs.
By the way. Since this is a two cylinder, 4 stroke with the crank throws 180 degrees apart, the engine fires twice in one revolution, then goes a complete revolution without firing. This means one cylinder fires, then the second one fires 90 degrees later. The cylinder that is missfiring is the first in that firing order.
Chuck
I got the new flywheels remounted and changed over to a carburetor that I had originally built for the engine. The carb is pretty basic, but it was readily available. The engine ran a little better, but still mostly on one cylinder. And, I couldn't get it to idle very slow.
So, I abandoned the carburetor and decided to go back to a vapor carb. I happened to have a glass jar that was 2 - 3 times taller than the pimento jar I had been using. And, it turns out, the pimento lid was the same screw size as the new bottle, so I just switched bottoms. This eliminated the splashing up into the intake tube and the engine smoothed out and ran pretty well, again, on one cylinder with the other cylinder firing intermittently. I increased the rocker arm clearance on both intake valves by quite a bit and this allowed me to slow the engine down to a pretty reasonable idle. The good cylinder was now firing ever time and the missing cylinder still fired intermittently. I removed the push rod from the intake valve on the good cylinder to see if I could get the engine to run on the missing cylinder. My thought was that maybe it wanted a leaner (or richer) mixture or maybe the other cylinder firing was interfering with the bad cylinder. However, I could barely get it to run on just the bad cylinder. I put it all back together and fired it up again. This time, I discovered when opened up the throttle a little, then I put a load on the engine by holding a rag against the flywheel, I could get it to fire on both cylinders pretty consistently at a pretty slow speed. I don't get it! But if all I have to do is put a load on the engine to make it run the way I want, so be it.
So here is what I've checked so far. Compression on both cylinders is excellent. Both intake valves are opening and closing at about the same position. Same with the exhaust valves. Ignition timing is identical for both cylinders. I'm beginning to think I might have a small air leak in the intake side of the bad cylinder. This is making run real lean and only firing ocassionally. Could be the manifold or it might be the valve stem on the intake valve. I might try putting a couple of drops of heavy gear oil on the valve stem and see if that seals it up temporarily. The other thing I haven't checked is the gap on the spark plugs.
By the way. Since this is a two cylinder, 4 stroke with the crank throws 180 degrees apart, the engine fires twice in one revolution, then goes a complete revolution without firing. This means one cylinder fires, then the second one fires 90 degrees later. The cylinder that is missfiring is the first in that firing order.
Chuck
