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

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74
75
76
KD425-2 Workshop Manual_cod. ED0053031750_1° ed_ rev. 00
Engine assembly

Pistons

Important
• 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
connecting 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 compression 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 piston 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) positions. 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:
0,10 ÷ 0,20 mm
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.
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