Engine Leakdown Test; Clutch Lever Hard To Pull In; Clutch Lever Soft Or Spongy; Rough Clutch Operation - Yamaha V star 1100 Owner's Manual

TROUBLESHOOTING

ENGINE LEAKDOWN TEST

Perform an engine leakdown test to pinpoint en-
gine problems caused by compression leaks. While
a compression test (Chapter Three) can identify a
weak cylinder, a leakdown test can determine where
the leak occurs. A cylinder leakdown test is made by
applying compressed air through the cylinder head
(with the valves closed), then measuring the leak
rate as a percentage. Under pressure, air leaks past
worn or damaged parts. You will need a cylinder
leakdown tester (Figure 6) and an air compressor to
perform this test.
1. Start and run the engine until it is warm. Then
turn the engine off.
2. Remove the air filter housing and surge tank as
described in Chapter Eight. Open and secure the
throttle at its wide-open position.
3. Set the No. 1 cylinder (rear) to top dead center
on its compression stroke as described in Valve
Clearance in Chapter Three.
4. Remove the spark plug from the No. 1 cylinder.
5. Thread the tester's 10 mm adapter into the No.
1 cylinder spark plug hole following the manu-
facturer's instructions. Then
leakdown tester onto the adapter. Connect an air
compressor hose onto the tester's fitting. Figure
6 shows a typical leakdown tester and its hose
connections.
WARNING
To prevent the engine from turning
over as compressed air is applied to
the cylinder, shift the transmission
into fifth gear and have an assistant
apply the rear brake. Remove any
tools attached to the end of the crank
shaft.
6. Apply compressed air to the leak tester and per-
form a cylinder leakdown test following the manu-
facturer's instructions. Read the percent of leak on
the gauge. Note the following:
a. For a new or rebuilt engine, a leak rate of 0 to
5 percent per cylinder is desirable. A leak rate
of 6 to 14 percent is acceptable and means the
engine is in good condition.
b. For a used engine, the critical rate is not the
leak percent for each cylinder but the differ-
ence between the cylinders. On a used engine,
a leak rate of 10 percent or less between cylin-
ders is satisfactory.
c. A leak rate exceeding 10 percent between cyl-
inders points to an engine that is in very poor
condition and requires further inspection and
possible engine repair.
7. After measuring the percent of leak, and with
air pressure still applied to the combustion cham-
ber, listen for air escaping from the following ar-
eas:
Use a mechanic's stethoscope to help
listen for air leaks in the following ar
eas.
a. Air leaking through the exhaust pipe indi-
cates a leaking exhaust valve.
b. Air leaking through the carburetor indicates a
leaking intake valve.
c. Air leaking through the crankcase breather
suggests worn piston rings or a worn cylinder
bore.
8. Remove the leakdown tester, and repeat these
steps for each cylinder.
connect the
Basic clutch troubles and their causes are listed in
this section. Clutch service procedures are in Chap-
ter Six.

Clutch Lever Hard to Pull In

If the clutch lever has become hard to pull in,
check the following:
1. Clutch cable requires lubrication.
2. Clutch cable improperly routed or bent.
3. Damaged clutch lifter bearing.

Clutch Lever Soft or Spongy

1. Air in the hydraulic system.
2. Low fluid level.
3. Leaking hydraulic system.

Rough Clutch Operation

1. Excessively worn, grooved or damaged clutch
hub and clutch housing slots.
2. Worn friction disc tangs.
43
NOTE
CLUTCH
2