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

Page 168
Image 168
Yamaha WR250FM service manual Piston ring, Side clearance, Limit, End gap, 10 ~ 0.40 mm 004 ~ 0.016