Need Piston

Pro-X is probably your best source for fractional oversized pistons.
Bear in mind that they need to be measured carefully along with a careful measurement of the bore to ensure adequate piston to wall clearance.

Originally posted by brentl
Thank you! What about those holes for the bridges ...they do anything?

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They allow fuel and oil to pass through from the crankcase cooling the bridge and minimizing the risk of a localized seizure at that point.

It's pretty tough to beat the Japanese OEM pistons for standard bore sizes. They are light, rugged, and fairly cheap.

I like the Wisecos that use their new forging process. They can produce a big bore 250F piston that weighs less than the OEM with this process. The Wisecos built using the old process tend to be a bit heavy and can shorten crank & rod life in a hurry.
To the best of my knowledge 250F & CRF450 pistons from Wiseco use this new process. Most of the YZF400 & 426 pistons I have seen appear to be the old heavier forgings. I haven't wighed the new 450F pistons yet to compare them.

I've used lots of Wisecos on YZFs with great luck, but it's important to respect crank maintenance intervals in this setup. Especially on the YZF400s which have fairly dodgy rods when they get a lot of hours on them.


JE & Ross also make excellent pistons that tend to weigh close to OEM even in big bore sizes.

I think Powroll has their excellent pistons built by Ross (Pam - feel free to correct me if I'm wrong here ;) )