I have been having some engine troubles that I cannot seem to correct despite having gone completely through the engine.
Would a worn cam lobe on a crankshaft affect the ignition?
I found that the side of the point that rides on the cam lobe has started to wear a groove into the lobe (due to my inexperience in knowing how to properly maintain the ignition system). This would probably account for why my engine slowly started to run rough at a certain throttle setting over time. Weird thing is it would run smooth most of the time. The problem was that it was just more unwilling to smooth out at full throttle. Does that make any sense? The first start of the day it would start right up. I would let it warm up for about two to three minutes. Then, I would slowly go to full throttle to check it out before flight. It would, as time went by, get worse and worse in cleaning out as it went to full throttle. It would run smooth as could be all the way to 3/4 throttle, then it would run rough and resist running smooth or advancing rpm. I could back off on the throttle and it would run smooth. Then I would try and advance the throttle and again at about 3/4 throttle, it would run rough again. If I played with the mixture needles, I could get it to work and it would run perfect the whole flight. But now it has got to the point that I can't ever get it to run smooth past 3/4 throttle. HELP!
George Curtis helped time my ignition and I found that it was set at 23 degrees BTD. That's just a little out of the window (17-13 degrees). So we set it to 15 degress BTD. I thought it would definitely change and run better, as it was timed wrong. And I was confident because George pointed out WHY the ignition timing had probably changed. I took the engine back home and tried it the next day. It didn't do a darn thing, darnit! It would run smooth till it got to 3/4 throttle. Then it would fight the additional throttle input by running rough. I played with the needles and found a way to make it run REAL rough and backfire. I must be talented. Anyway, frustrated, I gave up till today. I tried today and I got it back to running great...except at 3/4 throttle on up. Actually, at first it ran right up to full throttle. I checked the high needle to make sure I wasn't too lean, then went back to half throttle for a minute. I had a quick thought: Maybe it's all good now. I advanced the throttle to full. As I got up to 3/4, it started running rough, as is now usual. I listened to it and felt the waves of frustration come over me. Then, for an unexplained reason and at 3/4 throttle, it just quit. So I am completely perplexed.
I rebuilt the carb twice. No luck.
I swapped the carb with the good running engine. No luck.
I rebuilt the entire ignition system. No luck.
I timed the ignition and put it at 15 degrees BTD.
I checked the point's gap and it's at .018.
I installed another brand new spark plug.
Still no luck.
I am at a complete loss as to what is wrong. The only thing that is left that I haven't replaced is the piston, crankshaft, and bearings. Everything else is either brand new (the ignition) or replaced (the carb).
If any of you have had experience with this or have any ideas, please help.
MarkDJ.