2-22 PERIODIC MAINTENANCE
Periodic Maintenance Procedures
Piston Ring End Gap Inspection
Place the piston ring [A] inside the cylinder [B], using the
piston to locate the ring squarely in place.
Set it close to the bottom of the cylinder, where cylinder
wear is low.
Measure the gap between the ends of the ring with a thick-
ness gauge [C]
If the gap is wider than the service limit, the ring is over-
worn and must be replaced.
Piston Ring End Gap
0.25 ∼ 0.45 mm (0.0098 ∼ 0.0177 in.)
Service Limit: 0.75 mm (0.030 in.)
Piston, Piston Pin, Connecting Rod Wear Inspection
Visually inspect the snap ring [A] still fitted in place.
If the ring shows weakness or deformation, replace the
ring. Also if the pin hole groove shows excessive wear,
replace the piston.
Measure the diameter of the piston pin [B] with a microm-
If the piston pin diameter is less than the service limit at
any point, replace the piston pin.
Using a cylinder gauge, measure the diameter of both of
piston pin holes [C] in the piston and the inside diameter
of the connecting rod small end.
If either piston pin hole diameter exceeds the service limit,
replace the piston.
If the connecting rod small end inside diameter exceeds
the service limit, replace the crankshaft assembly.
Check the needle bearing [D].
The rollers in a needle bearing normally wear very little,
and wear is difficult to measure. Instead of measuring, in-
spect the bearing for abrasion, color change, other dam-
If there is any doubt as to the condition of a needle bear-
ing, replace the bearing and piston pin.
Piston Pin Diameter
17.995 ∼18.000 mm (0.7085 ∼ 0.7087 in.)
Service Limit: 17.96 mm (0.707 in.)
Piston Pin Hole Diameter
18.001 ∼ 18.011 mm (0.7087 ∼ 0.7091 in.)
Service Limit: 18.08 mm (0.712 in.)
Small End Inside Diameter
22.003 ∼ 22.012 mm (0.8663 ∼ 0.8666 in.)
Service Limit: 22.05 mm (0.868 in.)
Exhaust Valve Clean and Inspect
Refer to Exhaust Valve (KIPS) section in the Engine Top