Yamaha VMX12H Supplementary Service Manual page 287

TROUBLESHOOTING
The following conditions may indicate damaged shaft drive components:
1. A pronounced hesitation or "jerky" movement
during acceleration, deceleration, or sustained
speed. (This must not be confuse with engine
surging or tansmission characteristics.)
2.
A "rolling rumble" noticeable a t low speed; a
high-piched whine; a "clunk" from a shaft
drive component or area.
/ -
3.
A locked-up condition of the shaft drive
mechanism; no power transmitted from
engine to rear wheel.
NOTE:
B,
Areas A,
ficult to diagnose. The symptoms are quite
subtle and difficult to distinguish from normal
motorcycle operating noise. I f there is reason
to believe these components are damaged,
remove the components for specific inspection.
Symptoms
and C above may be extremely dif-
SHAFT DRIVE
Possible Causes
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.
foreign object lodged between moving
parts.
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