fastbshee Posted October 15, 2013 Report Share Posted October 15, 2013 I have a 421 cheetah cub on gas and when I first took it out never had the spark plug start backing out before until last weekend I have the power head with 23 CC custom cut domes and my timing is on plus two.basically trying to troubleshoot and see what could be causing this problem. can anyone help me thanks Quote Link to comment Share on other sites More sharing options...
fappy'97 Posted October 15, 2013 Report Share Posted October 15, 2013 What fuel you running? Compression? Who cut these 23cc domes? Quote Link to comment Share on other sites More sharing options...
Surfrjag Posted October 15, 2013 Report Share Posted October 15, 2013 Check that your getting good fuel flow and floats are set properly Quote Link to comment Share on other sites More sharing options...
WINDYCITYJOHN400 Posted October 15, 2013 Report Share Posted October 15, 2013 Keyway airleak? Quote Link to comment Share on other sites More sharing options...
fastbshee Posted October 15, 2013 Author Report Share Posted October 15, 2013 My compression is 150 psi bout sides and I'm running 93 pump gas. Brandon at wildcard racing cut the domes for me. Quote Link to comment Share on other sites More sharing options...
Surfrjag Posted October 15, 2013 Report Share Posted October 15, 2013 Keyway is on the left side windy Are my instructions to difficult? Lol Quote Link to comment Share on other sites More sharing options...
m671054 Posted October 15, 2013 Report Share Posted October 15, 2013 Drive gear keyway? i would call that rightside Quote Link to comment Share on other sites More sharing options...
oldskool Posted October 16, 2013 Report Share Posted October 16, 2013 I would try better fuel at 150psi. I had a deto problem with 93 octane and 150psi. (stock cylinders) Quote Link to comment Share on other sites More sharing options...
m671054 Posted October 16, 2013 Report Share Posted October 16, 2013 Trinity spark plug lock ftw!!!!! Quote Link to comment Share on other sites More sharing options...
Surfrjag Posted October 16, 2013 Report Share Posted October 16, 2013 I dunno why I was thinking flywheel keyway. drive keyway usally leaks oil and smokes a ton out of that side. either way I would still check that your getting good fuel flow by clearing out the gas cap vent and checking float height on both carbs. leakdown with tell you if its an airleak 1 Quote Link to comment Share on other sites More sharing options...
hitman392 Posted October 16, 2013 Report Share Posted October 16, 2013 Spark plug lock is junk (no offense) but you'll only be masking a real problem.. the plug backing out is from the harmonics of detonation.. that could severely damage your engine.. Quote Link to comment Share on other sites More sharing options...
Jereme6655 Posted October 16, 2013 Report Share Posted October 16, 2013 do a leakdown test. it will ensure that your not detonating from being lean.... Then do another compression test. Make sure your holding the throttle all the way open and kick until that needle stops moving. If both those check out good.......grab your self a 6"x6" piece of plexi-glass, some greese, and a drill bit. Pull your domes. Drill a hole just off to the side of the center of the plexi-glass. Then put a spark plug in the dome and press it to the glass so that the drilled hole is semi near the sealed lip of the dome. Then fill with water until you can see that there is no air bubble AND that the water is not coming out from being too full. This is how you check the cc of a dome. Not doubting brandons abilities.....but we're all human and all make mistakes sometimes. Doubt its a problem from him.....that's why this is the last option. Quote Link to comment Share on other sites More sharing options...
Finch Posted October 16, 2013 Report Share Posted October 16, 2013 since you didnt have probs before i doubt the dome is the issue. If its anything like here and has gotten colder and ya havnt hanged your jetting you could be running it too lean. id check that and a leak down. Quote Link to comment Share on other sites More sharing options...
m671054 Posted October 16, 2013 Report Share Posted October 16, 2013 do a leakdown test. it will ensure that your not detonating from being lean.... Then do another compression test. Make sure your holding the throttle all the way open and kick until that needle stops moving. If both those check out good.......grab your self a 6"x6" piece of plexi-glass, some greese, and a drill bit. Pull your domes. Drill a hole just off to the side of the center of the plexi-glass. Then put a spark plug in the dome and press it to the glass so that the drilled hole is semi near the sealed lip of the dome. Then fill with water until you can see that there is no air bubble AND that the water is not coming out from being too full. This is how you check the cc of a dome. Not doubting brandons abilities.....but we're all human and all make mistakes sometimes. Doubt its a problem from him.....that's why this is the last option. please explain this process on a dome that is stepped for a stroker motor Quote Link to comment Share on other sites More sharing options...
Finch Posted October 16, 2013 Report Share Posted October 16, 2013 Well you'd minus the 2 mm step and the area of the bore fo say a 4 mill. But for this 421 cub doesn't need stroker domes as the height needed is in the cyls. But just finding a cc won't solve all dome issues squish/band/angle can all play a rule. But where its a new problem not from day one I doubt its a dome issue. Quote Link to comment Share on other sites More sharing options...
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