If you have a lot of Carbon build up or suspect that,,,,,Take off-out the air filter, while at a fast Idle, warmed motor, take a spritzer bottle of water... CAREFULLY using the FINE spray into the venture and keep the motor running fast,,,,, That should get out the built up carbon in the cyl and piston tops...
I'm not saying to squirt water in any UN controlled amount ,into the engine BUT only using a fine misty spray..
Too Much liquid of any kind in a cylinder can cause a compression problem, Bending/Breaking the rod or crank..
Liquid does NOT compress smaller in size.... so careful
If you have ever had a water (head gasket) leak in a gas water cooled motor,,,,,When you replaced the gasket and it apart, You will notice NO carbon build up in that cyl. IF run with the leak into that cyl for a while...
signed....BUBBIE