3-10
Cleaning/Inspecting Piston Ring
Grooves
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.
Measuring Piston-Ring End Gap
(Installed)
1. Place each piston 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.
KM452
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
specifications, the piston pin must be replaced.
ATV-1070
2. Inspect and measure the connecting rod small end.
If the measurement exceeds specifications, the
connecting rod must be replaced (see Servicing
Center Crankcase Components in this section).
3. 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.
CC397D
2. Measure the corresponding piston diameter at a
point 18 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 be within specifications.
Installing Piston Rings
1. Install ring expander (4) in the bottom groove of
the piston; then install the thin oil rings (3) over
the expander making sure the expander ends do
not overlap. Stagger the end gaps of the upper and
lower thin oil rings according to the illustration.
NOTE: Note the direction of the exhaust side of
the piston (5) for correct ring end gap orientation.
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.
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