within the cylinder after the plug has been in
The spark plug recommended by the factory
is usually the most suitable for your machine.
For low speed riding. or when riding in cold
weather. a plug one step hotter may be
preferable. Refer to Table 3 at the end of the
chapter for the recommended spark plug.
Ensure [he spark plug used has the
correcr thread reach
thread reach too short will cause the
esposed threads in the cylinder head to
accutnulate carbon, resulting in stripped
cvlinder head threads when the proper
plug is installed. Too long a reach tnav
cuusr plug/piston contact and serious
1. Grasp the spark plug lead as near to the plug
as possible and pull it off the plug. Clear away
any dirt that has accumulated in the spark plug
D~rt could full Into the cyl~nders when
ret7zoved, causing ser~ous
2. Remove the spark plug with a spark plug
Inspect the spark plug carefully. Look for
broken center porcelain, excessively eroded
electrodes and excessive carbon or oil fouling
(refer to Figure 3 in Chapter Two as a plug
"reading" aid). If deposits are light the plug
may be cleaned with a wire brush or in a spark
plug sandblast cleaner, but the price of new
plugs is cheap insurance for high power and gas
mileage. Check the spark plug gasket. If it's
completely flattened, install a new one.
Never sandblast an oily or wet plug. The
grit will stick to the plug and later drop
into the engine. After sandblasting a
plug, clean it thoroughly.
4. Ifthe plug is reusable, file the center and side
electrodes flat. Less voltage is required to jump
the gap when the electrode corners are sharp.
5. Measure the gap with a round wire spark
plug gauge (Figure 61). The gauge should just
be able to pass through the gap. Adjust the gap
by bending the side electrode only. The gap
should be 0.024-0.028 in. (0.6-0.7 mm).
Apply a small a m o u n t of anti-sieze
compound to the plug threads. Don't use oil or
grease-they'll turn to pure carbon and make
the plug harder to get out the next time.
I f you're going to adjust the valve
clearance, leave the spark plugs out until
you're finished. It will be easier to turn
the engine over precisely.
7. Clean the seating area on the cylinder head
and thread the plug in by hand until it seats.
Then tighten the plug 1/8 to 1/2 turn with a
spark plug wrench. If you use a torque wrench,
the proper torque is 10 ft.-lb. (1.4 mkg).
AIR SUCTION VALVES
Models imported in the U S . are equipped
with a simple air suction system to minimize
exhaust emissions. The air suction valves (reed
valves) allow clean intake air to be sucked into
the exhaust ports during exhaust vacuum
pulses. This helps to complete combustion of
unburned hydrocarbons in the exhaust system.
The air suction valves also prevent exhaust
gas from backing up and flowing into the air
cleaner. If that should happen, you would have
an unplanned and unwanted EGR (exhaust gas
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