01 yz 250 rebuild problems

hey new to the forum so hope i'm posting in the right place. i'll try to keep it short and sweet. 01 yz 250 just bought everything to rebuild it. everything was going smoothly when we put the piston into the cylinder and tightened down the cylinder/jug the piston seizes in the sleeve, every time. loosen the bolts and the piston free's up....anyone have any insight on this? :thumbsup::banghead:

Did you forget the base gasket?

are you torquing them down in sequence? how is he thrust? how is the ring gap? is this a sleeved cyl or plated?

oversized piston?

When the cylinder is loose, will the piston go completely up and down?

Double check your ring end gap!!

It sounds like your bore clearance is very tight.

Sounds like something isn't allowing the piston to come all the way up. You got the head-gasket/o-ring in there, right? Did the previous owner have 2 base gaskets in there by any chance?

gasket is on there perfect, its a sleeved cyl. brand new just got back from the machine shop. tried torquing them down every which way possible. soon as the bolts get snug the piston freezes up in the sleeve.

but yes when its placed on there loose piston moves up and down perfectly fine...

How does your ring end gap look?

how would i check that?

Put the rings in the cyl and push the piston in to square them up. You could torque the jug and insert the piston to see where it binds. Is there any chance the piston is in backwards and hanging up on the ex port?

Make sure you check it at the top, middle and bottom of the cylinder. Call wiseco and ask them for the correct gap. It should be somewhere around .015"

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