Yamaha T135SE Service Manual page 70

MEASURING THE COMPRESSION PRESSURE
6. Install:
9 compression gauge 1
1
Compression gauge
90890-03081
7. Measure:
9 compression pressure
Out of specification
and (d).
Compression pressure
(at sea level)
Minimum
490 kPa (4.9 kg/cm
Standard
560 kPa (5.6 kg/cm
Maximum
630 kPa (6.3 kg/cm
a. Set the main switch to "ON".
b. With the throttle wide open and push the
"START" switch, then crank the engine until
the reading on the compression gauge sta-
bilizes.
w
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
measure again.
Refer to the following table.
Compression pressure
(with oil applied into the cylinder)
Reading
Higher than with-
out oil
Same as without
oil
3-16
http://www.motorcycle.in.th
CHK
ADJ
→ Refer to steps (c)
2
, 70 psi)/at 500 r/min
2
, 80 psi)/at 500 r/min
2
, 90 psi)/at 500 r/min
Diagnosis
Piston ring(s) wear
→→
or damage
Repair.
Piston, valves, cyl-
inder head gasket
or piston possibly
→→
defective Repair.