Compression Pressure Measurement - Yamaha YFM250XL(C) Service Manual

3

COMPRESSION PRESSURE MEASUREMENT

IGNITION TIMING CHECK/
5.Install:
Timing plug
6.Detach:
Timing light
Inductive tachometer
COMPRESSION PRESSURE
MEASUREMENT
NOTE:
Insufficient compression pressure will
result in performance loss.
Before measuring the compression pres-
sure, the valve clearance should be
adjusted.
Refer to "VALVE CLEARANCE ADJUST-
MENT" section.
1.Place the machine on a level place.
2.Remove:
Spark plug
3.Measure:
Compression pressure
**********************************
Measurement steps:
Install the Compression Gauge 1.
Compression gauge:
P/N. YU-33223, 90890-03081
Adapter:
P/N. YU-33223-3, 90890-04082
Crank over the engine with the electric
starter (be sure the battery is fully
charged) with the throttle wide-open until
the compression reading on the gauge
stabilizes.
WARNING
When cranking the engine, ground the
spark plug lead to prevent sparking.
Check readings with specified levels (see
chart).
Compression pressure (at sea level):
Standard: 900 kPa (9.0 kg/cm
Minimum: 800 kPa (8.0 kg/cm
Maximum: 1,000 kPa (10 kg/cm
3 - 18
INSP
ADJ
2
, 128 psi)
2
, 114psi)
2
, 142 psi)