Connecting Rods; Piston Rings - Pistons - Piston Pins - Kohler KD 425-2 Workshop Manual

4
20
21
22
23
- 28 -
Checks and overhaul

Piston rings - Pistons - Piston pins

Check the wear of piston rings by fitting them into the cylinder
through the lower end and measuring the end gap (fig.20). The
values should be:
Piston ring
Compression
Oil scrapper
Check that the rings move freely in the grooves and check the
ring/groove clearance using a feeler gauge (fig.21).
If the clearance exceeds the values shown in the table, renew
the piston and the piston rings.
Piston ring
1st Compression
2nd Compression
3rd Oil scrapper
Important
• Piston rings must always be renewed after dismantling the
piston.
Piston diameter check: The diameter of the piston must be
measured at approximately 18 mm from the base (fig.22).
Engine
KD 425-2
Check the clearance between cylinder and piston, if it is greater
than 0.120 mm both cylinder and piston must be replaced.
Assembly clearance between piston pin and piston in
millimetres:
Fitting mm
0,003 ÷ 0,013

Connecting rods

The connection between the connecting rod small end and the
wrist pin is without a bushing. Assembly clearance between
connecting rod small end and piston pin in millimetres:
Ø Piston pin
Engine
mm
KD 425-2 21,997 ÷
Checking parallelism between the two axes of the connecting
rod (fig.23):
1. Fit the wrist pin in the hole in the small end of the connecting
rod and fit a calibrated pin into the big end (with bush fitted).
KD425-2 Workshop Manual_cod. ED0053031750_1° ed_ rev. 00
Fitting mm Max. wear mm
0,30 ÷ 0,50
0,80
0,25 ÷ 0,50
Max. wear mm
A = 0,22
B = 0,18
C = 0,16
Diameter mm
84,910 ÷ 84,940
Max. wear mm
0,050
Assy.
clearance
mm
22,002 0,023 ÷ 0,038
Max wear
mm
0,070