3-22 ENGINE
CYLINDER BORE
Inspect the cylinder wall for any scratches, nicks or other dam-
age.
If anything unusual is found, replace the upper crankcase/cylin-
der.
Measure the cylinder bore diameter at six places.
Cylinder bore:
Standard: 36.005 – 36.015 mm (1.4175 – 1.4179 in)
PISTON AND PISTON RING
PISTON DIAMETER
Measure the piston outside diameter at 5 mm (0.2 in) height
from the skirt with a micrometer.
If the measurement is less than the service limit, replace the pis-
ton.
Piston diameter:
Service Limit: 35.885 mm (1.4128 in)
09900-20202: Micrometer (25 – 50 mm)
PISTON-TO-CYLINDER CLEARANCE INSPECTION
Subtract the piston diameter from the cylinder bore diameter.
(3-21)
If the piston-to-cylinder clearance exceeds the service limit,
replace the upper crankcase/cylinder or the piston, or both.
Piston-to-cylinder clearance:
Service Limit: 0.120 mm (0.0047 in)
PISTON RING TO GROOVE CLEARANCE
Measure the side clearances of the 1st and 2nd piston rings with
the thickness gauge.
If any of the clearances exceeds the limit, replace both the pis-
ton and piston rings.
Piston ring to groove clearance:
Service Limit (1st): 0.180 mm (0.0071 in)
(2nd): 0.150 mm (0.0059 in)
Piston ring groove width:
Standard (1st): 1.01 – 1.03 mm (0.0398 – 0.0405 in)
(2nd): 1.21 – 1.23 mm (0.0476 – 0.0484 in)
(Oil): 1.51 – 1.53 mm (0.0594 – 0.0602 in)
Piston ring thickness:
Standard (1st): 0.97 – 0.99 mm (0.0382 – 0.0390 in)
(2nd): 1.17 – 1.19 mm (0.0461 – 0.0469 in)
09900-20803: Thickness gauge
09900-20205: Micrometer (0 – 25 mm)
5 mm
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