Measuring The Compression Pressure - Yamaha 2009 XP500Y TMAX Service Manual

Spark plug
13 Nm (1.3 m·kg, 9.4 ft·lb)
TIP
Before installing the spark plug, clean the spark
plug and gasket surface.
9. Connect:
• Spark plug
10.Remove:
• Bottom cowling
Refer to "GENERAL CHASSIS" on page 4-1.
EAS20710
MEASURING THE COMPRESSION
PRESSURE
The following procedure applies to all of the cyl-
inders.
TIP
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 3-4.
2. Remove:
• Bottom cowling
Refer to "GENERAL CHASSIS" on page 4-1.
3. Start the engine, warm it up for several min-
utes, and then turn it off.
4. Disconnect:
• Spark plug cap
5. Remove:
• Spark plug
ECA13340
NOTICE
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.
6. Install:
• Compression gauge "1"
Compression gauge
90890-03081
Engine compression tester
YU-33223
7. Measure:
• Compression pressure
Out of specification → Refer to steps (c) and
(d).
Standard compression pressure
(at sea level)
1400 kPa/360 r/min (199.1
psi/360 r/min) (14.0 kgf/cm²/360
r/min)
Minimum–maximum
1220–1570 kPa (173.5–223.3 psi)
(12.2–15.7 kgf/cm²)
M MMM M MMM M M MMM M
a. Turn the main switch to "ON".
b. With the throttle wide open, crank the engine
until the reading on the compression gauge
stabilizes.
TIP
The difference in compression pressure be-
tween cylinders should not exceed 100 kPa (1
kg/cm², 14 psi).
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 min-
imum specification, pour a teaspoonful of en-
gine oil into the spark plug bore and measure
again.
Refer to the following table.
3-10
ENGINE
1
M MMM M M MMM M M MMM M MMM