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Need Piston

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Posted by: brentl

I need a slight oversize piston foe an 01 RM250.

I want to get one of those that are a few hundreths of a mm over to take up a little wear in my bore ( last time I had it apart there was about three and a half thou w/new piston)

Does Vertex ,Wiseco, or Suzuki OEM matter?

Can I get an oversize in Suzuki?What about Pro Lite or LA sleeve?

I am just looking for a no problem piston thet will last for motocross use. Dont want to get a weak one that shatters ..do I?

If Eric Gorr or Rich would like to comment I will listen.

I havent seen much discussion on this. If you guys think it does not matter then by all means say so. The stocker has little holes in it to "cool/lubricate?" the intake bridges , if a replacement hasn't got these do I add them?


Posted by: Rich Rohrich

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.


Posted by: brentl

Thank you! What about those holes for the bridges ...they do anything?


Posted by: Rich Rohrich

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


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.


Posted by: EdLennon

Rich,

Would that be your recommendation as well for the 4-strokes?

Thanks for all of your input,
Ed


Posted by: Rich Rohrich

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 )


Posted by: NO HAND

This is getting too interresting, may I ask a few questions about this. Just to clear the rumors.
Quote:
Originally posted by Rich Rohrich
It's pretty tough to beat the Japanese OEM pistons for standard bore sizes. They are light, rugged, and fairly cheap.
I had heard on the forum, the OEM was not a good choice because it was too loose and you could experience piston slap sooner than expected.


Quote:
Originally posted by Rich Rohrich
I like the Wisecos that use their new forging 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...
How can we find more info about this. Is there a way to know by the label on the box ex. say like the old pro tru, pro lite? What is so different with this new forging process?

Where can we find more info on Ross' pistons and what makes them excellent pistons?

I'm almost ambarassed to ask that many questions, but about all MXers have to buy pistons sooner or later and we rarely know on whan guidelines to support our choice from one brand to the other.
Many thanks!



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