Engine Inspection; Measuring The Compression Pressure - Yamaha N MAX GPD150-A 2015 Service Manual

EAS20041

ENGINE INSPECTION

EAS30249
MEASURING THE COMPRESSION
PRESSURE
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 3-5.
2. Start the engine, warm it up for several min-
utes, and then turn it off.
3. Remove:
• Front side cover (right)
Refer to "GENERAL CHASSIS (2)" on page
4-4.
• Footrest board assembly (right)
Refer to "GENERAL CHASSIS (5)" on page
4-12.
4. Disconnect:
• Spark plug cap
5. Remove:
• Spark plug
ECA20470
NOTICE
Before removing the spark plug, use com-
pressed air to blow away any dirt accumulat-
ed in the spark plug well to prevent it from
falling into the cylinder.
6. Install:
• Compression gauge "1"
• Extension "2"
Compression gauge
90890-03081
Engine compression tester
YU-33223
Extension
90890-04136
2
7. Measure:
• Compression pressure
Out of specification → Refer to steps (c) and
(d).
Standard compression pressure
(at sea level)
Minimum–Maximum
▼ ▼▼▼ ▼ ▼▼▼ ▼
a. Turn 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 min-
imum specification, pour a teaspoonful of en-
gine oil into the spark plug bore and measure
again.
Refer to the following table.
Compression pressure (with oil applied into the
cylinder)
Reading
Higher than without oil
Same as without oil
▲ ▲▲▲ ▲ ▲▲▲ ▲
8. Install:
1
• Spark plug "1"
Spark plug
5-1
ENGINE INSPECTION
1800 kPa/860 r/min (18.0
kgf/cm²/860 r/min, 256.0 psi/860
r/min)
1570–2020 kPa/860 r/min (15.7–
20.2 kgf/cm²/860 r/min, 223.3–
287.3 psi/860 r/min)
▼ ▼▼▼ ▼ ▼ ▼▼▼ ▼ ▼ ▼▼▼ ▼
Diagnosis
Piston ring(s) wear or
damage → Repair.
Piston, valves, cylinder
head gasket or piston
ring(s) possibly defec-
tive → Repair.
▲ ▲▲▲ ▲ ▲ ▲▲▲ ▲ ▲ ▲▲▲ ▲
13 Nm (1.3 m·kgf, 9.4 ft·lbf)
▼ ▼▼▼ ▼ ▼▼▼
▲ ▲▲▲ ▲ ▲▲▲