Compression Pressure Measurement - Yamaha F4 Service Manual

INSP
ADJ
1
GENERAL

Compression pressure measurement

NOTE:
Insufficient compression pressure will re-
sult in performance loss.
1. Check:
9 Valve clearance
Out of specification ® Adjust.
Refer to "VALVE CLEARANCE AD-
JUSTMENT" section.
2. Start the engine and let it warm up for
several minutes.
3. Turn off the engine.
4. Remove:
9 Spark plug
cC
Before removing the spark plug, use com-
pressed air to blow away any dirt accumu-
lated in the spark plug well to prevent it
from falling into the cylinder.
5. Set:
Compression gauge 1
9
Compression gauge:
YU-33223/90890-03160
6. Measure:
Compression pressure
9
Measurement steps:
8 Fully open the throttle grip and choke.
8 Rotate the crankshaft by pulling recoil
starter quickly several times and check
reading on the compression gauge.
NOTE
Pull the recoil starter fast and firmly with
the decompressor not in operation at
above 600 r/min.
w
Before cranking the engine, remove the
spark plug from the plug cap, and ground
the spark plug lead to prevent sparking.
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