Checking The Piston Ring; Checking The Piston Clearance - Yamaha YZ125 2009 Owner's Service Manual

3. Check:
• Free play (when the piston pin "1" is in place
in the piston "2")
There should be no noticeable for the play.
Free play exists→Replace piston pin and/or
piston.
4. Install:
• Small end bearing
• Piston pin
Into the small end of connecting rod.
5. Check:
• Free play
There should be no noticeable free play.
Free play exists → Inspect the connecting
rod for wear/Replace the pin and/or con-
necting rod as required.

CHECKING THE PISTON RING

1. Install:
• Piston ring
Into the cylinder.
Push the ring with the piston crown.
2. Measure:
• End gap
Use a thickness gauge "1".
Out of limit → Replace.
Ring end gap (installed):
Standard
0.5–0.7 mm (0.020–
0.028 in)
CYLINDER HEAD, CYLINDER AND PISTON
<Limit>
1.2 mm (0.047 in)
4-22
3. Measure:
• Side clearance
Use a thickness gauge "1".
Out of limit → Replace piston and/or ring.
Side clearance:
Standard
0.035–0.070 mm
(0.0014–0.0028 in)
Check at several points.

CHECKING THE PISTON CLEARANCE

1. Calculate:
• Piston clearance
Out of limit→Replace piston, and piston ring
and/or cylinder.
Refer to "Cylinder" and "Piston".
PISTON CLEARANCE = CYLINDER BORE -
PISTON DIAMETER
<Limit>
0.1 mm (0.004 in)