Kohler 17.5hp idles but stalls at full throttle

[acfair10]

John Deere L110 Kohler 17.5 engine will start and run at low throttle. When throttle is increased quickly it starts to miss and backfire and stalls unless throttle is returned to minimum level. If increased slowly it will not stall at full throttle.
engine has 500 hours and has worked great until this point. I worked the mower extremely hard the day prior. Long wet grass To the point it wanted to stall out. (I know this was stupid and I’ve definitely learned my lesson). However mower finished job. The following day I ran the tractor without engaging the mower deck with no issue for 3 hours. As soon as I engaged the mower deck it stalled. When I restarted the engine I had this issue. If I slowly increased the throttle to max and I originally could run at full throttle with no load. If I go from low throttle to high quickly it would stall after backfiring multiple times.
so far I have tried the following:
New gas
Fuel filter
Carborator
solenoid under the carb
Fuel pump
Spark plug (extremely fouled)
Checked voltage on stator
Battery
Please Help.
Thank you for reading

 

[bertsmobile1]

The two things you have missed is setting the valve lash unless it is a Command engine with hydraulic lifters and cleaning the fuel tank

 

[acfair10]

John Deere L110 Kohler 17.5 engine will start and run at low throttle. When throttle is increased quickly it starts to miss and backfire and stalls unless throttle is returned to minimum level. If increased slowly it will not stall at full throttle.
engine has 500 hours and has worked great until this point. I worked the mower extremely hard the day prior. Long wet grass To the point it wanted to stall out. (I know this was stupid and I’ve definitely learned my lesson). However mower finished job. The following day I ran the tractor without engaging the mower deck with no issue for 3 hours. As soon as I engaged the mower deck it stalled. When I restarted the engine I had this issue. If I slowly increased the throttle to max and I originally could run at full throttle with no load. If I go from low throttle to high quickly it would stall after backfiring multiple times.
so far I have tried the following:
New gas
Fuel filter
Carborator
solenoid under the carb
Fuel pump
Spark plug (extremely fouled)
Checked voltage on stator
Battery
Please Help.
Thank you for reading

The problem ended up being the ignition coil. $70 part and about 5 minutes to change out. It’s back up and running like a top.