Yamaha Rhino YXR66FAV Owner's Manual page 72

Each full throttle acceleration sequence
should be followed with a substantial rest pe-
riod for the engine by cruising at lower r/min
so the engine can rid itself of the temporary
build up of heat. If any abnormality is noticed
during this period, consult a Yamaha dealer.
0–10 hours:
Avoid continuous operation above half throt-
tle. Allow a cooling off period of five to ten min-
utes after every hour of operation. Vary the
speed of the vehicle from time to time. Do not
operate it at one set throttle position.
10–20 hours:
Avoid prolonged operation above 3/4 throttle.
Rev the vehicle freely but do not use full throt-
tle at any time.
After break-in:
The vehicle can now be operated normally.
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