91
POWERHEAD
CYLINDER/CRANKCASE/PISTON
6
Measure the cylinder bore in the thrust and axial
directions at the three position depths.
Check for the following:
• Difference between the measurements at the
three positions (taper).
• Difference between the thrust and axial mea-
surements (out-of-round).
Cylinder bore wear (difference):
• Service limit – 0.0039 in. (0.100 mm)
If the wear (difference) exceeds the service limit,
rebore or replace the cylinder.
To check the piston to cylinder clearance, mea-
sure the following items:
• Cylinder bore at 20 mm elevation from the gas-
ket surface at a right angle to the crankshaft pin.
• Piston skirt diameter at 5 mm elevation from the
skirt end.
Piston to cylinder clearance:
• Standard – 0.0007 to 0.0013 in. (0.018 to 0.033
mm)
• Service limit – 0.0039 in. (0.100 mm)
If the clearance exceeds the service limit, replace
the piston and/or the cylinder, or rebore cylinder.
Cylinder bore:
• 1.8898 to 1.8904 in. (48.000 to 48.015 mm)
Piston skirt diameter:
• 1.8888 to 1.8894 in. (47.975 to 47.990 mm)
Oversize piston and piston rings are marked as
shown.
Piston
First and Second Ring
Oil Ring
006075
006076
006078
1
2
3
Oversize I.D. Mark
0.50 mm 50
Oversize Piston I.D. Mark
Oversize I.D. Mark
0.50 mm 50
Oversize First and Second Ring I.D. Mark 006080
Oversize I.D. Mark
0.50 mm Blue paint
Oversize Oil Ring I.D. Mark 006081
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