Drive Train; Troubleshooting; Checking Noises - Yamaha YXR70FX Service Manual

EBS00155

TROUBLESHOOTING

The following conditions may indicate damaged shaft drive components:
Symptoms
1. A pronounced hesitation or "jerky" move-
ment during acceleration, deceleration or
sustained speed. (This must not be con-
fused with engine surging or transmission
characteristics.)
2. A "rolling rumble" noticeable at low speed; a
high-pitched whine; a "clunk" from a shaft
drive component or area.
3. A locked-up condition of the shaft drive train
mechanism, no power transmitted from the
engine to the front and/or rear wheel.
TIP:
_
Areas A, B, and C above may be extremely difficult to diagnose. The symptoms are quite subtle and
difficult to distinguish from normal vehicle operating noise. If there is reason to believe these compo-
nents are damaged, remove the components and check them.
TROUBLESHOOTING

DRIVE TRAIN

A. Bearing damage.
B. Improper gear lash.
C. Gear tooth damage.
D. Broken drive shaft.
E. Broken gear teeth.
F. Seizure due to lack of lubrication.
G. Small foreign objects lodged between the
moving parts.
EBS00156

CHECKING NOISES

1. Investigate any unusual noises.
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(a).A "rolling rumble" noise during coasting,
acceleration, or deceleration. The noise
increases with front and/or rear wheel
speed, but it does not increase with higher
engine or transmission speeds.
Diagnosis: Possible wheel bearing damage.
(b).A "whining" noise that varies with accelera-
tion and deceleration.
Diagnosis: Possible incorrect reassembly,
too-little gear lash.
NOTICE
_
Too little gear lash is extremely destructive
to the gear teeth. If a test ride following
reassembly indicates this condition, stop
riding immediately to minimize gear dam-
age.
7 - 1
DRIV
Possible Causes
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