Johnson K-40 pistons

[james-davis]

anyone ever try using newer piston in old engine? K-40 has same bore size as 9.9 Evinrude, if dome and wrist pin are the same why couldn’t I cut port in piston skirt like K-40 has or would it be too off balance? mine are too far gone and no one seems to have replacements.

[Tom]

The K-40 is an opposed twin, with exhaust out the bottom. So the deflector on top of the piston goes side to side across the piston. The 9.9 is an alternate twin, with exhaust to the side, so the deflector goes up and down. So even if they fit, and the distance from the crown to the pin is the same, the motor won’t run.

T

[james-davis]

Glad you said something, didn’t think about that, had to read up on deflector, back to trying to find right ones.

[Author]

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