Kohler 26 Hp backfire on decell

[PABresnick]

I have a Kohler Comand 26 Hp with less than 100 hours that started out by dieseling at shut off and has now progressed to stumbling on accelleration and also back firing with a large flame out the exhaust when you reduce the throttle. Head gaskets were done last year to eliminate the oil consumption problem and the carb has been cleaned but I found no dirt or varnish. Kohler is sending me a new accellerator pump diaphragm but the old one was fine. The fly wheel key is also good. Carb is not adjustable on mixture but float level is good. This is a model cv25s on a Craftsman tractor that is 3 years old. I bought it used so I have no warranty and parts can get expensive if I start guessing. Any help or ideas would be great. I figure its getting extra fuel on decell to shoot the flame.

[khouse]

You can get a backfire if there is a hole in the muffler or the muffler gaskets are bad.

[PABresnick]

Exhaust is good and there are no leaks.

[khouse]

Maybe it's running hot? Have you dechaffed the engine? On my 25 command the carb was cleaned twice with no effect. Kohler sent a brand new one to put on and it runs great now.

[selph]

I have the Kohler Command 25 HP on my Grasshopper. It also does this. Now it will run fine until it gets warm (20-30 min.) and the starts backfiring really bad. It does it worse under full throttle. Any ideas? The problem may be the same as yours :( Dave

[khouse]

Does either one of your engines have a lot of tappet noise? It will be a light to heavy clicking or ticking noise from the lifters not pumping up.

[selph]

No tappet noise at all on mine. dave

[danzig]

Sounds like a faulty coil. The backfire could happen if the exaust is too rich from all the fuel not being burned up. Mine does this but i know it has a hole in the muffler.