CYLINDER AND PISTON

ENG

Piston pin

1.Inspect:

Piston pin

Blue discoloration/grooves Replace, then inspect the lubrication system.

2.Measure:

Piston pin-to-piston clearance

Measurement steps:

Measure the outside diameter (piston pin) a.

If out of specification, replace the piston pin.

Outside diameter (piston pin): 15.991 ~ 16.000 mm (0.6296 ~ 0.6299 in)

Measure the inside diameter (piston) b.

Inside diameter (piston): 16.002 ~ 16.013 mm (0.6300 ~ 0.6304 in)

Calculate the piston pin-to-piston clear- ance with the following formula.

Piston pin-to-piston clearance = Inside diameter (piston) b – Outside diameter (piston pin) a

If out of specification, replace the piston.

Piston pin-to-piston clearance: 0.002 ~ 0.022 mm

(0.0001 ~ 0.0009 in) <Limit>: 0.07 mm (0.003 in)

ASSEMBLY AND INSTALLATION Piston ring and piston

1.Install:

Piston ring Onto the piston.

NOTE:

Be sure to install the piston rings so that the manufacturer’s marks or numbers are located on the upper side of the rings.

Lubricate the piston and piston rings liberally with engine oil.

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Image 169
Yamaha WR250FM service manual Piston pin, Inside diameter piston 16.002 ~ 16.013 mm 0.6300 ~ 0.6304