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Need help
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Posted by: vance757

I have a trx250r and need a new piston kit
it is 2.50(.100 over) what displacement does that
put me at and what piston should i go with?

Posted by: C-LEIGH RACING

A 2.50 stamped on the top of the piston is a 68.50mm size.
CC wise, 34.25 Xs 34.25 Xs 72 Xs 3.1416 =s 265341.11 ccs
not quite a 265 & a 1/2 cc engine.
What build is this, it use a old 85/86 model TRX piston, a 86 YZ or a CR250R flat top piston.
Neil

Posted by: vance757

its the trx quad version...
it have spacer plate on the cylinder and
the piston is wiseco just found that out

Posted by: C-LEIGH RACING

If your going to bore next size, Pro-X has a # 0291 cast piston .110 over a 66.75mm or the next size up from Wiseco a # 526MO6900 .120 over 69.00mm.
Neil