25 hp Kohler command engine

[Carlos onate]

i just got a 02 grasshopper mower with a 25 hp Kohler command and is running but when i do a full throttle and turn it down i get some explosion and when i pull the clutch switch at full throttle wants to shutdown and some times it does, I have replaced the sam ignition to a regular coils, also install a new carburetor, new spark plugs i took both heads to a shop, replace head gaskets, bleed lifters, 180 compression on both cylinders, leak down test very good i disconnect al wiring and power the fuel solenoid and still doing it, the timing dots on cam gear and crank gear are fine and key way on flywheel too, let me know if you have some ideas, thanks.

 

[sgkent]

when an engine is turned off at full throttle, unburned fuel and air continue to flow thru the engine, and when that combination hit a hot exhaust sometimes it ignites causing a bang. Let it idle and cool down for 30 seconds to a minute before turning it off. The engine will last longer.

 

[Ozcub]

Idle down to half throttle and then turn it off , thats what the book says to do anything else is WRONG

 

[ILENGINE]

when an engine is turned off at full throttle, unburned fuel and air continue to flow thru the engine, and when that combination hit a hot exhaust sometimes it ignites causing a bang. Let it idle and cool down for 30 seconds to a minute before turning it off. The engine will last longer.

Idle down to half throttle and then turn it off , thats what the book says to do anything else is WRONG

Kohler procedure it to turn it off at half to full throttle because on Kohler engines the fuel shutoff solenoid doesn't block the idle circuit. So by turning off at idle you are allowing the engine to pull in unburnt fuel, but the engine will demand fuel through the high speed jet as it winds down and will not be available if the throttle is open to allow the throttle butterfly to fully open.

And to the OP. In rare cases the afterfire effect can be caused by the muffler itself. Did you install a new OEM carb of a aftermarket Amazon style carb. Your issues could also be related to a slightly lean run condition, and I don't know if your engine has the accelerator pump on the carb, which if not working correctly can cause the engine to die when placed under sudden load.

 

[slomo]