BRP Johnson 4HP, Service Manual, Page: 100 / 185

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POWERHEAD
PISTON PIN / CONROD / CRANKSHAFT
PISTON PIN / CONROD / CRANKSHAFT
Piston pin clearance
To check the clearance, measure the following items.
•
Piston pin outside diameter in the thrust and axial direc-
tions.
•
Piston pin hole diameter in the thrust and axial directions.

Micrometer
Dial calipers
Pin clearance in piston pin hole:
Standard: 0.006 – 0.019 mm (0.0002 – 0.0007 in)
Service limit: 0.040 mm (0.0016 in)
Pin clearance in conrod small end:
Standard: 0.006 – 0.019 mm (0.0002 – 0.0007 in)
Service limit: 0.050 mm (0.0020 in)
If the clearance exceeds the service limit, replace the piston,
the piston pin and/or the conrod assembly.
Piston pin outside diameter:
Standard: 17.995 – 18.000 mm (0.7085 – 0.7087 in)
Service limit: 17.980 mm (0.7079 in)
Piston pin hole diameter:
Standard: 18.006 – 18.014 mm (0.7089 – 0.7092 in)
Service limit: 18.030 mm (0.7098 in)
Conrod small end inside diameter:
Standard: 18.006 – 18.014 mm (0.7089 – 0.7092 in)
Service limit: 18.040 mm (0.7102 in)