Measuring The Compression Pressure - Yamaha VMX12 2001 Service Manual

CHECKING THE IGNITION TIMING/

MEASURING THE COMPRESSION PRESSURE

b. Check that the stationary pointer a is within
the firing range b on the generator rotor.
Incorrect firing range → Check the ignition
system.
NOTE:
@
The ignition timing is not adjustable.
@
4. Install:
• timing plug
EAS00065
MEASURING THE COMPRESSION
PRESSURE
The following procedure applies to all of the
cylinders.
NOTE:
@
Insufficient compression pressure will result in
a loss of performance.
@
1. Measure:
• valve clearance
Out of specification → Adjust.
Refer to
CLEARANCE".
2. Start the engine, warm it up for several min-
utes, and then turn it off.
3. Disconnect:
• spark plug cap
4. Remove:
• spark plug
CAUTION:
@
Before removing the spark plugs, use com-
pressed air to blow away any dirt accumu-
lated in the spark plug wells to prevent it
from falling into the cylinders.
@
5. Install:
• compression gauge 1
Compression gauge
90890-03081
6. Measure:
• compression pressure
Out of specification → Refer to steps (c)
and (d).
3 - 17
CHK
ADJ
"ADJUSTING THE VALVE