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Kohler bore

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Why is .030 the largest oversize bore Kohler allows in it's K series cast iron engines? What possible harm can an extra .010 (.040 over) do to the cylinder? Can aftermarket pistons be bought in .040 over? Thanks for any and all answers. Dick

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The overbore size has to do with two things. 1.) Engine balance. As the bore gets larger the piston gets heavier. The crank must then be re-balanced to compensate or the engine will suffer from tremendous vibration. 2.) Overheating. Larger pistons mean more displacement and higher compression, resulting in more heat. The cooling fins and fan are not designed for this. A friend of mine used to build pro stock pulling tractors, and he would bore a 16 Hp Kohler approximately .180 oversize. He had the engines re-balanced and they were not run continuously for any long periods of time.

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