changing A piston 2001 yz250

[Joe Kovarik]

Dose anyone know a web site that can take me set by set on how to change a piston?
Or anybody on this site,I know I can do it just never did one before.
I just bought a yz250 and want to change it before I go riding
THANKS FOR ANY HELP
JOE

 

[BSWIFT]

First, I recommend that you get a manual. Next, checkout the parts break down at Yamaha.com.
Remove the seat, tank/shrouds, and exhaust. Drain the radiators and remove them. Remove the head/motor mount and then the bolts holding the head.
Using the parts diagram, remove the power valve linkage and the nuts holding down the cylinder. You may need to use a mallet or deadblow hammer to dislodge the cylinder. Do not use a screwdriver or pry bar. Lift the cylinder off and grab hold of the piston to not let it hit the case.
VERY IMPORTANT: Place shop rags all around the connecting rod to prevent ANYTHING from dropping into the case!!!!!!!!
Remove the circlips holding the wrist pin and PRESS the wrist pin out of the piston. Check all of the tolerences and clean the power valve, pipe, and head. Check the cylinder for unusual wear. Before final installation, put your new ring into the cylinder, pushing it in with the new piston(ring not on the piston) and check the end gap.
Reassemble in reverse order.
Trick: You can use a strip of a plastic milk jug and a rubberband to help compress the ring on the piston when stabbing the cylinder onto the piston. Once the rings are in the cylinder, you can cut the rubberband.
Most everything is straight forward. Pay close attention when removing the powervalve linkage and reinstall carefully. Use all new gaskets and torque to factory specs. Take careful not of the torque wrench that you use and not over torque the nuts and bolts.
VERY IMPORTANT: Place shop rags all around the connecting rod to prevent ANYTHING from dropping into the case!!!!!!!! Especially when installing the circlips!!!!

A service manual is very important and will give you every step that you need, as well as, the torque specs.
Good luck.

 

[Joe Kovarik]

BSWIFT,
Thanks for the info. You are right I need a manual .
THANKS AGAIN
JOE