250-500cc Piston Clearance

I have tried to search this before asking, but apparently I am blind and can not find in my manual the piston clearance specs for 2002 WR250. I noticed some piston manufacturers have one size fits all at 66.4mm, but Wossner lists oversizes also. I want to give the Wossner pistons a try, and want to order the best fit without going too tight after getting cylinder measurements. Want to triple check everything and get it right. This will be my first top end job.

what size is on the top of your existing piston?
wossner do 4 piston sizes the first three are only a .0thou different.
there is a .06 clearence on them, are you getting the cylinder nikasiled-sleeved or just putting new piston in?
if its being sent off suply the first piston to the company and they will hone it to suit.

Few terminology issues, I'm sure the difference in wossner's pistons is one TENthousanth between them, and the clearance may be .007, which sounds very loose for a fresh bore.....

From my 09 WR250 manual: Piston clearance should be 0.04-0.06mm. Wear limit 0.08mm. Bore measured 10 mm from top. Piston measured 24mm from the bottom of skirt.

Also, measure the bore with a bore gauge front to back and side to side, if you want accuracy. Calipers don't cut it. Measure the piston with a micometer.

Dude, you gotta be careful, those numbers are really whacky and somebody might read this and try to build a motor based on it.

As per the manual for my 2012, the piston-to-cylinder clearance should be 0.04-0.06mm (0.0015-0.0024 inches).

Thank you for the info. I finally found the correct info in my manual. I haven't taken it apart yet, but I don't know if there will be a piston size or not. The PO said it was rebuilt with Wiseco about 2004 or so, and not used since 07. I'm going to put a fresh one in no matter what. I do a ln't have a good shop nearby, but I have a relationship with a local automotive machine shop who will help me mic the cylinder dimentions.

sorry i missed a zero. yup 0.06 is right as per wossner site, my bad