31
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. Inspect and measure the connecting rod small end. If
the measurement exceeds specifications, the con-
necting rod must be replaced (see Servicing Center
Crankcase Components).
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.
ATV-1085B
2. Install the compression rings (1 and 2) so the letter
on the top surface of each ring faces the dome of the
piston. Rotate the rings until the ring end gaps are on
directly opposite sides of the piston according to the
illustration.
726-306A
CYLINDER ASSEMBLY
NOTE: If the cylinder cannot be trued, it must be
replaced.
Cleaning/Inspecting Cylinder
1. Wash the cylinder in parts-cleaning solvent.
2. Inspect the cylinder for pitting, scoring, scuffing,
warpage, and corrosion. If marks are found, repair
the surface using a cylinder hone.
CAUTION
Incorrect installation of the piston rings will result in
engine damage.
