Vintage Dirt Bike Q & A

i have a 81cr250r cyl bored .50 over no scoring just low comp 70lp how many more over sizes can i go book only list .50 but i see wesco pistons .80 over i am going to send it to a shop should i have them get the piston or is it cheper and safer to go back to a new sleve

If Wiseco makes an .080 oversize piston, I imagine that's the absolute cheapest way to go. I assume you've measured the piston and found it's under the minimum spec diameter, so that just a ring replacement won't be enough?

If it were my bike and I was planning on keeping it, I'd consider have U.S. Chrome plate the liner wuth Nikasil to the standard or 1st-oversize bore (they can add about .025" of Nikasil for an .050" bore reduction). This is a much better solution than replacing the cast-in liner with a press-fit one, in my opinion. Cost is about $270.

Ray

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'74 CR125M (175cc), '75 MR175, '82 RM250Z, '08 YZ250F, '14 Zero FX electric, '14 Zero MX electric, '18 Alta MXR electric