LUBRICATION, MAINTENANCE AND TUNE-UP
Install t h e fuel tank; see
in Chapter Seven.
A cylinder cranking compression check is
but it is the quickest
way tb check the internal condition of the
engine: rings, valves, head gasket, etc. It's a
good idea to check compression at each
tune-up, write it down and compare it with the
reading you get at the next tune-up. This will
help you spot any developing problems before
they cost too much repair money.
Ride the bike to warm it up fully. Make sure
the choke is OFF.
Remove the spark plugs.
Insert the tip of a compression gauge into
the spark plug hole, making sure it seals fully
4. Turn the kill switch off, hold the throttle
wide open and crank the engine several
revolutions until the gauge gives its highest
reading. Record the number and repeat for the
When interpreting the results, the actual
reading is not as important as the difference
from the last check and the difference between
cylinders. Individual gauge calibrations vary
widely. A significant drop (more than 15 psi)
since the last check (made with the same gauge)
may indicate engine top end problems.
If the compression is 125 psi or more and
there is less than a 15 psi difference between
cylinders, compression is normal. If either
cylinder reads less than about 125 psi, check
your readings with a recently calibrated gauge.
It may be time to rebuild the top end (rings and
To tell the source of a problem, pour about a
teaspoon of motor oil into the spark plug hole.
Turn the engine over once to distribute the oil,
then take another compression reading. If the
compression returns to normal, the valves are
good, but the rings are worn. If compression
does not increase, the valves may be damaged.
Several months of inactivity can cause
problems and a general deterioration of bike
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