Yamaha WR250FM service manual Piston and piston ring, Piston pin puller set YU-1304/90890-01304

CYLINDER AND PISTON

ENG

REMOVAL POINTS

Piston and piston ring

1.Remove:

•Piston pin clip 1

•Piston pin 2

•Piston 3

NOTE:

•Put identification marks on each piston head for reference during reinstallation.

•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 difficult to remove, use the piston pin puller set 4.

Piston pin puller set:

YU-1304/90890-01304

CAUTION:

Do not use a hammer to drive the piston pin out.

2.Remove:

• Piston ring 1

NOTE:

Spread the end gaps apart while at the same time lifting the piston ring over the top of the piston crown, as shown in the illustration.

INSPECTION

Cylinder and piston

1.Inspect:

•Cylinder and piston walls

Vertical scratches → Replace cylinder and piston.

2.Measure:

•Piston-to-cylinder clearance

Measurement steps: 1st step:

•Measure the cylinder bore “C” with a cylin- der bore gauge.

NOTE:

Measure the cylinder bore “C” in parallel to and at right angles to the crankshaft. Then, find the average of the measurements.

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