TP-5393 9/93 Scheduled Maintenance 3-15
Cylinder Head Service
After each 500 hours of operation, the cylinder heads
should be taken off the engine and serviced. Remove
carbon deposits from combustion chamber in head.
Scrape and remove carbon with a sharp piece of wood
or plastic. Wood or similar material is suggested to
avoid scratching aluminum surfaces of the cylinder
head. Always use new cylinder head gaskets. Make
sure head bolts are tightened in the proper sequence
and to the torque value specified. See Figure 3-17.
NOTE
If the engine is operated on leaded fuel or under certain
conditions, such as continued light load or relatively
constant speed, carbon may build up more rapidly. If
there are early indications of this, such as heavy
depositsofcarbon onsparkplugelectrodes,servicethe
heads more frequently. A 250 hour service interval is
suggested under these conditions.
3 7
8
1
4
9
6
2
5
1
2
3
Figure 3-17. Cylinder Head Fastener Tightening
Sequence
1. Use new gaskets when reinstalling heads.
2. Tightening sequence
3. Tighten head bolts to 15-20 ft. lbs. (20-27 Nm.)
Valve Service
After each 500 hours of operation (or sooner if a loose
valve is detected), check clearance between the valve
stems and tappets. The engine must be stopped and
cooled to normal ambient temperatures to accurately
gauge and adjust valve clearances. Use the following
procedure to adjust.
IMPORTANT:
The piston must be at top dead center (TDC) of the
compression stroke to measure valve-to-tappet
clearance. By rotating the flywheel and observing the
valves and tappets for movement, it can be determined
if a cylinder is at TDC.
If, for example, the flywheel is rotated and movement is
noticed in the #2 side valve box—the opposite cylinder
(#1 side) will be at TDC and valve-to-tappet clearance
can be measured.
Rotatingtheflywheelonecompleterevolution(360°)will
then cause movement in the #1 side valve box—the #2
side cylinder will be at TDC, enabling measurement of
valve-to-tappet clearance for that side.
CLEARANCE SPECIFICATIONS
Intake
0.003-0.006 in. (0.076 mm - 0.152 mm)
Exhaust
0.011-0.014 in. (0.279 mm - 0.355 mm)
1. Rotate the flywheel and look into the valve boxes.
The valves and tappetswill move in only one ofthe
boxes. Measure the valve-to-tappet clearance for
the cylinder in which no movement was
observed—use a flat feeler gauge.
2. Rotate the flywheel 360° and measure the
valve-to-tappet clearance for the remaining
cylinder.
3. If clearance is too small, or too large, remove
generator set and take to an authorized Kohler
service dealer.
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