38
Measuring Piston Skirt/
Cylinder Clearance
1. Using a slide gauge and a dial indicator or a snap
gauge, measure the cylinder bore diameter in three
locations from top to bottom and again from top to
bottom at 90° from the first measurements for a total
of six measurements. The trueness (out-of-round-
ness) is the difference between the highest and low-
est reading. Maximum trueness (out-of-roundness)
must not exceed specifications.
CC127D
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 surface plate.
3. Place the cylinder on the surface plate covered with
#400 grit wet-or-dry sandpaper. Using light pressure,
move the cylinder in a figure eight motion. Inspect
the sealing surface for any indication of high spots.
A high spot can be noted by a bright metallic finish.
Correct any high spots before assembly by continu-
ing to move the cylinder in a figure eight motion
until a uniform bright metallic finish is attained.
Inspecting Cam Chain Guide
1. Inspect cam chain guide for cuts, tears, breaks, or
chips.
2. If the chain guide is damaged, it must be replaced.
Honing Cylinder
1. Wash the cylinder in parts-cleaning solvent.
2. Inspect the cylinder for pitting, scoring, scuffing, and
corrosion. If marks are found, repair the surface
using a #320 grit ball hone.
NOTE: To produce the proper 60° cross-hatch pat-
tern, use a low RPM drill (600 RPM) at the rate of 30
strokes per minute. If honing oil is not available, use a
lightweight petroleum-based oil. Thoroughly clean
cylinder after honing using soap and hot water. Dry
with compressed air; then immediately apply oil to
the cylinder bore. If the bore is severely damaged or
gouged, replace the cylinder.
CAUTION
Incorrect installation of the piston rings will result in
engine damage.
CAUTION
Water or parts-cleaning solvent must be used in con-
junction with the wet-or-dry sandpaper or damage to
the sealing surface may result.
Содержание Altera 300
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