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I need good technical advice regarding which type of oversize (+20) I should use. The pistons presently fitted are of the long skirt type,make unknown,and weigh 302 grams.I have obtained a new pair, made by JP, however, these weigh 370 grams and have short skirts.As my engine has the older type crankshaft and the alloy capped con-rods,I am concerned that the balance will be wrong and excessive loads will be placed on the bottom end.
Any suggestions ?
Terry
You are absolutely right t…
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You are absolutely right to be concerned about the weight difference. Many of the replacement pistons, on the market, are much heavier than the originals. JP & GPM most notably. Lots of owners have fitted new pistons without checking and ended up with teeth rattling vibes. A few extra grams are not going to be a problem but adding nearly 70g on for each piston is around a 25% change. Probably requiring a crankshaft rebalance.
Checkout the other recent Heavy Twins thread about pistons. There is lots of good advice within it.