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V A L V E / T A P P E T G A P A D J U S T M E N T
Valve/Tappet Gap
Adjustment
After approximately one hour of operation,
tappet gap adjustment may be necessary.
When you check the valves, lubricate the
moveable parts. Also make sure the screw is
in tight before making adjustments to valves.
Adjust the valves to a clearance of .03mm to
.10mm (.002 to .004 in) using the supplied
gauge. The valves must be adjusted with the
engine cold due to thermal expansion.
note: Valves must be in the compression
stroke or closed position as shown in
the following figure. When adjustment
is completed, make sure you tighten the
lock nut.
Adjust between
Tappet Adjustment
0.03 – 0.10mm (.002 in – .004 in)
Gauge
(0.1mm Max.)
Screw
How to adjust
Remove the plug and the rocker arm cover
and revolve the propeller slowly clockwise by
hand. The intake side rocker arm stops, and by
turning it, the piston reaches the compression
top dead center (TDC).
In that position, adjust with the included
gauge and hexagonal wrench so tappet gap
may be set to almost zero when the engine is
in the compression stroke. If the gauge can
enter (a limit gauge with a 0.1 mm thickness),
the clearance is at maximum and needs
adjustment, adjust between 0.03 and 0.10mm
(0.002 to 0.004 in.) After the gap is checked,
tighten the locknut securely. Do not over-
tighten.
The tappet gap is the most important factor
in the maintenance of 4-stroke engines,
and operation with an excess clearance will
degrade performance. In particular, a large gap
aggravates abrasion of the tappet and the cam
and also increases the unusual sound.
27
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