Re: Re: Re: Continuing missing F-20 engine saga

Posted by Bill Smith on December 12, 2003 at 18:10:47 from (63.147.130.83):

In Reply to: Re: Re: Continuing missing F-20 engine saga posted by Pete L on December 12, 2003 at 07:22:18:

After reading your re-post here, now you got me second guessing. Do you know for a fact that it is randomly missing on all 4 cylinders? Which would lead me to beleive the problem might be on the intake end of things (carb problem or govenor out of adjustment) since you have eliminated mag trouble. Valve problems generally only affect the cylinders with the valve problems (unlikely to be all 4 cylinders unless you ground the valves at the wrong angle, or all the seats are bad, or the valves that you ground should of been rejected or something of that nature). Back to the popping noise you are hearing. A bad valve (say an intake valve) is burnt (has a hole and does not seat completely all the way around) will make a light popping noise that can be heard out the intake (especially if air breather pipe disconnected). Is what you are slightly hearing is that cylinder actually firing on that bad valve. The cylinder may still have enough compression to fire the piston but the popping noise will be there on every fire on that cylinder witch means the noise will be timed to that cylinder and as fast as the engine is running. This noise is almost identicle to the noise you can make by opening your lips while trying to suck air in through your mouth, or whipping mashed potatoes (not a loud backfire noise). Same thing will happen on exhaust valve, only the noise will come out the exhaust instead of intake. A backfire (out the exhaust) only happens when cylinder doesn't fire, blows unburnt fuel mixture out the exhaust, and is then ignited by hot exhaust parts before it gets out the exhaust system. If I was you, I would double check timing to make darn sure it is correct (since problem appears with spark adjustment). I would then rule out any carb or governor problems before taking the head off simply because those problems are more easily fixed in the process of elimination for figuring out what is wrong. You ussually notice problems with govenor adjustment with throttle adjustment. I remember how baffling my F-20 was. I finally got it running good. Be sure to use the process of elimination. My trouble was, I had about three things wrong and was trying to pin point the problem. I am not sure I helped you any but I hope I did.

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• Re: Re: Re: Re: Continuing missing F-20 engine sag Pete L 20:16:44 12/14/03 (0)

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