Measuring The Compression Pressure - Yamaha XG250 Service Manual

7. Install:
Spark plug
●
Spark plug
18 Nm (1.8 m•kg, 13 ft•lb)
NOTE:
Before installing the spark plug, clean the spark
plug and gasket surface.
8. Connect:
Spark plug cap
●
EAS20710
MEASURING THE COMPRESSION
PRESSURE
The following procedure applies to the cylinder.
NOTE:
Insufficient compression pressure will result in a
loss of performance.
1. Measure:
Valve clearance
●
Out of specification → Adjust.
Refer to "ADJUSTING THE VALVE CLEAR-
ANCE" on page 3-3.
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
●
ECA13340
CAUTION:
Before removing the spark plugs, use com-
pressed air to blow away any dirt accumulat-
ed in the spark plug wells to prevent it from
falling into the cylinders.
5. Install:
Compression gauge "1"
●
Extension "2"
●
Compression gauge
90890-03081
Engine compression tester
YU-33223
Extension
90890-04082
2
6. Measure:
Compression pressure
●
Out of specification → Refer to steps (c) and
(d).
Compression pressure (standard)
1200 kPa/300 r/min (12 kgf/cm
300 r/min)
Compression
mum)
1300 kPa/300 r/min (13 kgf/cm
300 r/min)
Compression pressure (minimum)
1050 kPa/300 r/min (10.5 kgf/cm
300 r/min)
▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼
a. Set the main switch to "ON".
b. With the throttle wide open, crank the engine
until the reading on the compression gauge
stabilizes.
EWA12960
WARNING
To prevent sparking, ground the spark plug
lead before cranking the engine.
c. If the compression pressure is above the
maximum specification, check the cylinder
head, valve surfaces and piston crown for
carbon deposits.
Carbon deposits → Eliminate.
d. If the compression pressure is below the
minimum specification, pour a teaspoonful of
engine oil into the spark plug bore and mea-
sure again.
Refer to the following table.
3-9
ENGINE
1
2
/
pressure (maxi-
2
/
2
/