Yamaha YZ250 Owner's Service Manual page 113

REMOVING THE PUSH ROD
1. Remove:
• Bolt (push rod) "1"
• Push rod "2"
Insert the set pin "3" included in owner's tool kit
to remove the bolt (push rod).
Be sure to use the set pin. If the set pin is
not used, the power valve constituent parts
will result in damage.
REMOVING THE PISTON AND PISTON RING
1. Remove:
• Piston pin clip "1"
Before removing the piston pin clip, cover the
crankcase with a clean rag to prevent the piston
pin clip from falling into the crankcase cavity.
2. Remove:
• Piston pin "1"
• Piston "2"
• Small end bearing "3"
Before removing each piston pin, deburr the
clip groove and pin hole area. If the piston pin
groove is deburred and the piston pin is still dif-
ficult to remove, use the piston pin puller set
"4".
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CYLINDER HEAD, CYLINDER AND PISTON
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Piston pin puller set:
YU-01304/90890-01304
Do not use a hammer to drive the piston pin
out.
3. Remove:
• Piston ring "1"
Take care not to scratch the piston or damage
the piston ring by expanding it more than nec-
essary.
CHECKING THE CYLINDER HEAD
1. Eliminate:
• Carbon deposits
Use a rounded scraper "1".
Take care to avoid damaging the spark plug
threads. Do not use a sharp instrument. Avoid
scratching the aluminum.
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