I'm hoping someone here may be able to help with a problem I'm having with this engine. Engine has about ~ 170 hours on it and about 8-10 yrs old.
The problem I'm having right now is when I try to start the engine the carb throat fills up with gas and fuel comes out the muffler. I also noticed gas being spit back through the carb, but not with enough force to blow up. I've had a long history with repairs on the engine, but for a while it did run fine. Here's the repair history roughly in this order from what I can recall:
* Replaced flywheel key (was sheared when I bought it)
* Cleaned and checked carb since mower sat for a while
* Mower ran fine for a while before stopping. However, the valve train (lifters) were noisy for a while and went away when warm)
* After running for several hours across several days, it stopped. Engine started dumping fuel out exhaust
* Took carb apart again, cleaned and checked bowl for gas and height (again) Needle valve appeared fine.
* Did compression check, OK given ACR on these engines. Did a leak down test and did notice air leakage through both valves and crankcase at TDC.
* Checked, cleaned and lapped valves. Installed new head gasket. I did note that clearance between rockers and valve stems was practically non-existent. Not sure if this is normal (engine has hydraulic lifters)
* At some point the engine wound up shearing another flywheel key. I have not cut any grass with the mower so nothing was hit.
* Mower sat 3-4 months before trying to start yesterday.
What I *think* might be wrong is either the ACR sticking, hydraulic lifter problems or some other carb issue. I'm not sure what to do next....