Yamaha YXR70FX Service Manual page 95

MEASURING THE COMPRESSION PRESSURE
4. Disconnect:
• spark plug cap
5. Remove:
• spark plug
NOTICE
_
Before removing a 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.
6. Attach:
• extension 1
• compression gauge 2
Compression gauge
90890-03081
Engine compression tester
YU-33223
Extension
90890-04082
7. Measure:
• compression pressure
Out of specification → Refer to steps (c)
and (d).
Compression pressure (at sea
level)
Minimum
392 kPa (3.92 kg/cm
Standard
450 kPa (4.50 kg/cm
Maximum
504 kPa (5.04 kg/cm
M MMM M MMM M M MMM M
a. Set the main switch to "ON".
3 - 11
CHK
ADJ
2
, 55.8 psi)
2
, 64.0 psi)
2
, 71.7 psi)
M MMM M M MMM M M MMM M MMM