Yamaha WR250FM Piston ring, Side clearance, Limit, End gap, 10 ~ 0.40 mm 004 ~ 0.016

CYLINDER AND PISTON

ENG

Piston ring

1.Measure:

•Ring side clearance

Use a feeler gauge 1.

Out of specification → Replace the piston and rings as a set.

NOTE:

Clean carbon from the piston ring grooves and rings before measuring the side clearance.

	Side clearance:
	Standard	<Limit>
Top ring	0.030 ~ 0.065 mm	0.12 mm
	(0.0012 ~ 0.0026 in)	(0.005 in)
2nd ring	0.020 ~ 0.055 mm	0.12 mm
	(0.0008 ~ 0.0022 in)	(0.005 in)

2.Position:

•Piston ring (in cylinder)

NOTE:

Insert a ring into the cylinder and push it approximately 10 mm (0.39 in) into the cylin- der. Push the ring with the piston crown so that the ring will be at a right angle to the cylinder bore.

a 10 mm (0.39 in)

3.Measure:

•Ring end gap

Out of specification → Replace.

NOTE:

You cannot measure the end gap on the expander spacer of the oil control ring. If the oil control ring rails show excessive gap, replace all three rings.

	End gap:
	Standard	<Limit>
Top ring	0.15 ~ 0.25 mm	0.50 mm
	(0.006 ~ 0.010 in)	(0.020 in)
2nd ring	0.30 ~ 0.45 mm	0.80 mm
	(0.012 ~ 0.018 in)	(0.031 in)
Oil ring	0.10 ~ 0.40 mm	—
	(0.004 ~ 0.016 in)

4 - 46