Yamaha YFM660FS Grizzly 4x4 Supplementary Service Manual page 330

TROUBLESHOOTING
CAUTION:
Too little gear lash is extremely destructive to
the gear teeth. If a test ride following reas-
sembly indicates this condition, stop riding
immediately to minimize gear damage.
c.A slight "thunk" evident at low speed opera-
tion. This noise must be distinguished from
normal machine operation.
Diagnosis: Possible broken gear teeth.
WARNING
Stop riding immediately if broken gear
teeth are suspected. This condition could
result in the shaft drive assembly locking
up, causing loss of control of the machine
and possible injury to the rider.
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2.Inspect:
Drained oil
G
Drained oil shows large amounts of metal
particles → Check the bearing for seizure.
NOTE:
A small amount of metal particles in the oil is
normal.
3.Inspect:
Oil leakage
G
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Inspection steps:
G
Clean the entire machine thoroughly, then
dry it.
G
Apply a leak-localizing compound or dry
powder spray to the shaft drive.
G
Road test the machine for the distance nec-
essary to locate the leak.
Leakage → Inspect the component housing,
gasket, and/or seal for damage.
Damage → Replace the component.
NOTE:
An apparent oil leak on a new or nearly new
G
machine may be the result of a rust-preven-
tative coating or excessive seal lubrication.
Always clean the machine and recheck the
G
suspected location of an apparent leakage.
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DRIV