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Hello, first time forum poster… rebuilding my 1990 KDX200 and I have to bore the cylinder due to damage. What is a good piston to purchase I can bore the cylinders to? Not wanting to go to much bigger than standard. Sizes & recommendations would help tremendously. Thanks in advance!

Welcome to kdxrider.net.

When new, the cylinder had a plated surface which is not able to be bored. Do you know if it is plated or if someone installed a cylinder sleeve?

KDXGarage wrote: ↑05:06 pm Oct 01 2022 Welcome to kdxrider.net.

When new, the cylinder had a plated surface which is not able to be bored. Do you know if it is plated or if someone installed a cylinder sleeve?

I brought the cylinder to a machine/cylinder shop today, & the guy told me it had a sleeve & was able to be bored. He asked me to get him the standard size along with the size of the new piston I plan to put in it. I’m just not sure with what piston to go with, or what size bore anybody would recommend. Anything in the right direction would help!

I'd buy a Wiseco piston in standard or stock size. Take him your new piston & cylinder so he can measure your piston & then machine your cylinder to match.

See if Wiseco still makes oversize pitons. It will show something like 20 thousandths or so. If it is scratched, the guy doing the boring should know how deep he needs to go, then get that sized piston. Make sure the piston does not hit the subvalves of the power valve system. They are close in the 1989 - 1994 KDX200.