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Craftsman w/ 20hp Kohler Running Rough


LawnSite Member
SE Texas
I fired up my Sears lawn tractor this morning and noticed after 10 minutes of mowing that the engine started missing and running very rough. It happens less with the blades disengaged, and more when under load.

Only thing I did differently this morning than normal was check the oil and add a bit to bring the level back into the good range (was just a hair low).

I've cleaned the air filter, but I can't determine what the problem might be.

Any suggestions?


LawnSite Fanatic
How long has it been since it had a tune-up and service ? Has it been set up over winter ? I would check the spark plugs first, One could be fouled.

Oh....Welcome to LawnSite....

Bill Kapaun

LawnSite Senior Member
Albany, Orygun
It could be the head gasket letting go although I'd expect to see some blue smoke with this.
As RESTROROB mentioned- tune up & has it sat.
It simply might be due for a couple new spark plugs.
IF it sat over the winter, you might have some water condensed in the fuel tank. It'll tend to collect on the bottom of the carb bowl. When the engine is placed under load, some of it gets picked up due to higher fuel flow through the carb. IF you have some Gas-Dri, throw a couple oz. in the tank. Fresh gasahol will do the same thing if you have that available, since alcohol absorbs water.