Coming to the hive mind for this one because it's driving me nuts.
I have an older John Deere zero turn mower with a liquid cooled Kawasaki v twin motor. It started to feel down on power and almost stalls out when the deck is first engaged. It really struggles through thick grass. It sounds like it's running on one cylinder but if I disconnect either spark plug it continues to run and sound the same. Both coils give a good spark and the compression is 170psi on both cylinders. I've changed plugs, air filer, swapped in a new coil and cleaned the carb all without making any appreciable difference. the deck bearings are in decent shape and the belt turns easily by hand. Next step is running the carb through my ultrasonic tank.
Any other ideas on this one? Am I chasing two problems? Am I missing something obvious?
I've seen the air cooled version fail head gaskets before with those symptoms, not sure if the water cooled ones can fail the same way. Had good compression numbers but one cylinder would blow combustion gas out the failed gasket when fuel was actually being burned.
Compression numbers suggest the valves are in adjustment and you don't have a failing compression release.
Clean the spark arrester in the exhaust and check that the governor is working properly. But it sounds like a potential carb or fuel pressure/filter issue. Those single carb for two cylinder setups can do funny things when enough fuel is supplied for a cylinder and a half worth of engine, but not enough to fuel both cylinders properly. How'd the old plugs look?
Id clean the carb for sure. Focus on the main jet (s) since thats where your fuel delivery comes from under load. Could be something as dumb as a partially blocked off jet from sitting or some crud in the tank.
