Pistons; Connecting Rods; Cylinders - Kohler KD 425-2 Workshop Manual

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74
75
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KD 425-2 Workshop Manual_cod. ED0053029360_1° ed_ rev. 00

Pistons

Lubricate the following parts with oil before mounting: the
piston pin, the piston, the cylinder and the big-end bearing
Fit the piston rings onto the pistons (fig.73) in the following order:
1. Chromed compression ring
2. Torsional compression ring (with internal bevel facing upward)
3. Expander oil scraper ring (external bevel facing upward).
Install the piston to the connecting rod, by pushind the wrist pin in,
without heading the piston.

Connecting rods

After having fitted the bearings into the big ends mount the connec-
ting rods to the crank journals pins; note that the pistons are marked
with an arrow showing the direction of rotation of the engine. The
combustion chamber, which is offset with respect to the central axis
of the piston, must be turned to face the injector nozzle side. Mount
the connecting rod big end cap ensuring that the reference numbers
are aligned with those punched on the connecting rod itself (fig.74).
Torque the bolts to:
kgm 3,6 ÷ 3,8 (Nm 35,3 ÷ 37,3)
Now fit the oil pan after first inserting the appropriate gasket between
the facing surfaces.

Cylinders

Before fitting the cylinders turn the piston rings so that the end gaps
are arranged at intervals of 120° with the end gap of the first com-
pression ring aligned with the axis of the wrist pin. The lower face of
the cylinders are chamfered to permit the easy insertion of the piston
rings. The operation can be simplified, however, using a normal pi-
ston ring compressor (p.n. 00365R0770) as shown in figure 75.
Mount the cylinders to the crankcase as shown in figure 76 and then
bring the pistons up to their respective TDC (top dead centre) posi-
tions. The following must now be checked:
1. that the dots punched on the flywheel (TDC) correspond to the
reference mark on the flywheel-housing
2. that the pistons protrude over the top surface of the cylinders
(fig.76) by a distance of:
This distance is adjusted with special shims that are inserted
between the bottom surface of the cylinder and the crankcase 0.1
- 0.2 - 0.3 mm.
ENGINE ASSEMBLY
0,10 ÷ 0,20 mm
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