timing problem,4 cylinder not firing,fuel in crank

I'm rebuilding a 1980 kz 750 4 and for the 4th time now trying to start her up to sync the carbs after several half ass ignitions @ high RPM she seems to jump timing before I can adjust vaccuum and @ this point continuing to turn her over fuel poors into the crank increasing volume oil level.Is the timing jumping out of sync causing fuel to dump into the crank? I thought I'd buy a new cam chain tensioner "APE w/ no spring" thinking it would resolve the timing coming out of sync but no. How tight should the cam chain tensioner be? I've done the clear tube carb float adjustment and they are perfect. I can't seem to dial in the idle adjustment and after checking the sparks #4 doesn't even seem to be firing.I'll attempt to set the timing again but this vicious cycle is getting old.I need help or suggestions please.I'm running keihin carbs with stage 3 jet kit,4-1 vance and hines and pods.Thanx Bryan

I will reply to the parts of ur issues that I can and others here will jump in as well.A "Stage 3" jet kit on an otherwise stock engine seems a bit much even with pods and a V and H.Try the stock jetting and see if that will fire off.I installed an APE tensioner and followed the factory print out,tightened with my fingers as tight as I could then backed out a quarter turn.No problems.Good luck.bj

bluferno wrote:

:...1980 KZ750 4...fuel pours into the crank increasing volume oil level....

Fuel in crankcase usually results from leaking float valve or improper float function, where carb either has no overflow circuit or an obstructed overflow circuit.

Good Luck!

I have not played with the jet kits, pods nor exhaust, but this quoted reasoning makes sense to me.




Patton wrote:

bluferno wrote:

:...1980 KZ750 4...fuel pours into the crank increasing volume oil level....

Fuel in crankcase usually results from leaking float valve or improper float function, where carb either has no overflow circuit or an obstructed overflow circuit.

Good Luck!