Yamaha GRIZZLY 660 YFM66FAV Owner's Manual page 88

WARNING
_
Always ride at a slow speed when the ATV is in
4WD-LOCK, and allow extra time and distance
for maneuvers.
All wheels turn at the same speed when the dif-
ferential is locked, so it takes more effort to
turn the ATV. The amount of effort is more the
faster you go. You may lose control and have
an accident if you cannot make a sharp
enough turn for the speed you are traveling.
_
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