Yamaha RAPTOR YFM660R Owner's Manual page 282

11. Add sufficient oil of the recommended type to
raise it to the correct level, and then install
and tighten the oil tank filler cap.
Recommended engine oil:
See page 10-2.
CAUTION:
_
G
In order to prevent clutch slippage (since
the engine oil also lubricates the clutch),
do not mix any chemical additives with the
oil or use oils of a grade "CD" or higher. In
addition, do not use oils labeled "ENERGY
CONSERVING II" or higher.
G
Make sure that no foreign material enters
the crankcase.
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