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Cylinder matching piston?

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so i pulled the Cylinder off my 06 250, i see a letter A on it, so i order up an A OEM piston kit from the local dealer, i open the packaging and theres a B stamped with ink on top of the new piston. But all the packaging all says on the code, part# then a capital A at the end, i mic'd the piston and the old one, looks identical from what i can tell.

Basically, does it matter or make a difference? i mean i know if you buy a wiseco its just the one size anyways...

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Sounds like you're okay here but I would call the company that you bought it from and speak with someone in shipping/parts just to be absolutely certain because obviously the wrong piston could cause you all sorts of hell. Nice catch good eye, most a-holes would just give it the "meh" and slap it in there.

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the more im looking at it i THINK im safe, i mean when i mic'd both of them, there identical in every way, so maybe the B shouldn't BE there, maybe an A in its place?. i mean on the packaging it says made in japan, so the dealers have no control over something like that other then letting yamaha in Japan know, i ringed the new one and put the cylinder on not catching and feels just right from what i can tell, i just hope i played my cards right on this one..

i guess just future reference if anyone comes across this lettering error.

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Lets say you started with "a". Now the cylinder is worn in and the "b" would probably be perfect anyway. But, like you noticed before, the sizes are so close as to not matter much. If I remember correctly, the size difference, between each letter is .01mm.

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The difference is so small between piston sizes that a B piston (or even a C piston) is still in the tolerance of clearance with a brand new A cylinder. Then add in the face that, as mentioned, your A cylinder has been used and therefor has some amount of wear to it. You will be fine with a B piston.

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