Yamaha WARRIOR YFM350X Owner's Manual page 170

Riding your machine requires skills acquired
through practice over a period of time.
Take the time to learn the basic techniques well
before attempting more difficult maneuvers.
Not recommended for children under 16 years
of age.
WARNING
A child under 16 should never operate an ATV
with engine size greater than 90cc. Use by
children of ATVs that are not recommended
for their age can lead to severe injury or death
of the child.
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