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Engine basics => Engine set up tips => Topic started by: RDJeff on November 09, 2011, 09:30:44 PM
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I just picked up my sixth FP40 on the auction site, and this one is different from the others in that there is a hole in the piston skirt. What have I got here? The hole is about 1/4" in diameter, and appears to be machined that way. I can see the rod ond pin through the hole. I'm used to older two-stroke motorcycles having holes in the piston skirts, but they are in the intake face, while this is visible throught the exhaust port. Interesting...
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Piston in backwards.
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So, why didn't I think of that? ???
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I have several FP 40s—both steel liner and ABN—and the only holes in the piston are for the wrist pin. None have a hole in the side of the piston.
I'm going to guess that it's been modified and the piston is in back to front.
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Not stock. FP pistons don't have that hole.
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Not stock. FP pistons don't have that hole.
Yes FP pistons did have that hole from OS in early motors
Randy
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It looks like I need to take apart some of my FPs in order to see what's what!
Randy, if the hole is standard on older engines, do you think my piston is in backwards?
Thanks everyone for the responses!
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yes the piston is more than likley in backwards, check the rod also if it has one side of the bottom "chamfered" put it toward the crankshaft
Randy
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Thanks Randy, I'll give it a look!