Service Manual

5-20 ENGINE TOP END
Cylinder, Piston
•
Cleanthepistonringgrooves[A]withabrokenpistonring
or other suitable tools.
CAUTION
Be careful not to widen the ring grooves. Damaged
ring grooves will require piston replacement.
Piston Ring and Ring Groove Wear
•
Clean the piston (see Piston Cleaning).
•
Visually inspect the piston rings and ring grooves.
If the piston rings are worn unevenly or damaged, replace
them with new ones.
If the ring grooves are worn unevenly or damaged, re-
place both the piston and the piston rings with new ones.
•
Measure the clearance between the top and second rings
and their grooves using a thickness gauge [A] as shown.
If the piston ring/groove clearance is greater than the ser-
vice limit, replace the piston with a new one.
Piston Ring/Groove Clearance
Service Limit:
Top 0.19 mm (0.0075 in.)
Second 0.20 mm (0.0079 in.)
NOTE
○
The oil ring is a three piece assembled ring. It is difficult
to measure the ring groove clearance and thickness,
visually inspect only.
•
Measure the piston ring thickness [A].
○
Use a micrometer to measure at several points around
the rings.
If any of the measurement are less than the service limit,
replace the entire set of rings with new ones.
Piston Ring Thickness
Service Limit:
Top 1.1 mm (0.043 in.)
Second 1.1 mm (0.043 in.)
NOTE
○
When using new rings in a used piston, check for un-
even groove wear. The rings should fit perfectly parallel
to the groove sides. If not, replace the piston with a new
one.