1984 Yamaha 115 bangs and misses @4000rpms

[LA3]

1984 Yamaha 115 bangs and misses @4000rpms. Motor runs great until 4000 rpms. Then starts making a metal to metal bang/clang sounds and breaks down. Missing. Like it has no oil or fuel or electrical short. But, I have no idea. Motor just started doing it and has never had a problem. Only thing I did was clean engine and then put back overboard. Run like a top anywhere below 4000rpms. It will push up to 5000 rpms and makes noise until I let off alittle bit. Help PLEASE.

 

[Ray Neudecker]

Re: 1984 Yamaha 115 bangs and misses @4000rpms

Excellent chance you have a fuel restriction. Check all lines for a loose connection. Squeeze bulb and look for leaks. If bulb does not stay firm and you don't see leaks, loosen two bolts on fuel pump and gently pull away slightly from block, squeeze bulb and see if leak is from pump. If so, replace the pump. Do not rebuild. Careful with the bulb squeezing, one hand only to simulate 6 lbs of pressure.