Checking Connecting Rod Small End; Gudgeon Pin Diameter - PIAGGIO 500 cc Service Manual

Thermal unit and timing system

Checking connecting rod small end

- Measure the connecting rod small end diameter by
means of a reamer.
Standard diameter: 22
N.B.: If the connecting rod small end diameter exceeds
the standard value, if it shows signs of wear or over-
heating, replace the driving shaft as described in Chap-
ter 8-Crankcase and Driving Shaft.

Gudgeon pin diameter

- Check the gudgeon pin outside diameter by means of
a micrometer.
Standard diameter: 22
- Calculate the connecting rod small end - gudgeon pin
allowance
Standard clearance: 0.015 - 0.029 mm
- Measure the piston support diameter
Standard diameter: 22
- Calculate the gudgeon pin - piston allowance.
Standard clearance: 0.001 - 0.010 mm
N.B.: The gudgeon pin housings are provided with 2
lubrication ducts. Therefore the diameter must be meas-
ured according to the piston axis
- Measure the piston outside diameter orthogonally to
the gudgeon pin axis.
- Perform the measurement as shown in the figure:
A = 43.2 mm
Piston diameter: 92 mm
7 - 10
+ 0.025
mm
+ 0.015
0
mm
- 0.004
+ 0.006 mm
+ 0.001
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