Yamaha VMX12H Supplementary Service Manual page 288

SHAFT DRIVE
6-49
Inspection Notes
lnrestigate any unusual noises
The following "Noises" may indicate a
mechanical defect:
a. A "rolling rumble" noise during coasting,
acceleration, or deceleration. The noise
increases with rear wheel speed, but it does
not increase with higher engine or trans-
mission speeds.
Diagnosis: Possible wheel bearing damage.
b. A "whining" noise that varies with accele-
ration and deceleration.
Diagnosis: Possible incorrect reassembly,
too-little gear lash.
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 damage.
A
slight "thunk" evident a t low speed
c.
operation. This noise must be distinguished
from normal motorcycle operation.
Diagnosis: Possible broken gear teeth.
Stop riding immediately if broken gear teeth
are suspected. This condition could result in
a locking-up of the shaft drive assembly,
loss
causing of control of the dike and possible
injury to the rider.
2. Inspect:
Drained oil
Drain plug shows large amount of metal.
Particles Check bearing fur seizure.
NOTE:
A small amount of metal particles in the oil i s
normal.