YZ250 top end question.

I'm going to do a top end job on my '01 YZ250 but I'm a rookie on the plated bore thing.  I don't have a problem with the top end.  I want to change it before I do since I have no idea how many hours the PO has on it.  I'm going to use an OEM piston.  So, am I safe to just buy a "D" piston, which is the largest OEM size for the YZ?  I was going to take it to a shop to do the hone (deglaze) and have them measure things and since the size differences in the OEM pistons are so small, the shop gave me the impression that if I brought them a "D" piston, they would hone to give the proper clearance since the plating on the bore IS thick enough to do this.  Is this the proper way to do this or is it not textbook but workable?


Most likely you will be just fine to run the d piston...the differences are so small that you shouldnt have a problem. I want to say the differences between a,b,c and d is like one and a half thousandths and it seems most cylinders are b size anyway and with any kind of hours on it d size should be ok...however you can not hone to get clearance..honing is just putting cross hatches back in the plating to make oil stick to the cylinder walls and prolong the life of your new topend.

Won't hurt to let them measure tho and make sure you Are within spec.

Edited by yzrider383

If you are going to take it to a shop to have them hone the cylinder then I would have them tell you what size you need after they inspect everything.  I had great luck with Hanson Racing with my sons YZ125 if you are in the north metro.  Great guy and he even gave me a great deal on the top end kit.

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