30
2. Remove each ring by working it toward the dome of
the piston while rotating it out of the groove.
CC400D
Cleaning/Inspecting Piston
1. Take an old piston ring and snap it into two pieces;
then grind the end of the old ring to a 45° angle and
to a sharp edge.
2. Using the sharpened ring as a tool, clean carbon from
the ring-grooves. Be sure to position the ring with its
tapered side up.
3. Using a non-metallic carbon removal tool, remove
any carbon buildup from the dome of the piston.
4. Inspect the piston for cracks in the piston pin, dome,
and skirt areas.
5. Inspect the piston for seizure marks or scuffing.
6. Inspect the perimeter of each piston for signs of
excessive “blowby.” Excessive “blowby” indicates
worn piston rings or an out-of-round cylinder.
Measuring Piston-Ring End Gap
(Installed)
1. Place each compression ring in the wear portion of
the cylinder. Use the piston to position each ring
squarely in the cylinder.
2. Using a feeler gauge, measure each piston-ring end gap.
Acceptable ring end gap must not exceed specifications.
CC280D
Measuring Piston Pin (Outside
Diameter) and Piston-Pin Bore
1. Measure the piston pin outside diameter at each end
and in the center. If measurement is not within speci-
fications, the piston pin must be replaced.
ATV-1070
2. Insert an inside dial indicator into the piston-pin
bore. The diameter must not exceed specifications.
Take two measurements to ensure accuracy.
ATV-1069
Measuring Piston Skirt/
Cylinder Clearance
1. Measure the cylinder front to back in six places.
CC127D
2. Measure the corresponding piston diameter at a point
15 mm above the piston skirt at a right angle to the
piston-pin bore. Subtract this measurement from the
measurement in step 1. The difference (clearance)
must not exceed specifications.
CAUTION
Improper cleaning of the ring-grooves by the use of the
wrong type of ring-groove cleaner will result in severe
damage to the piston.
