Yamaha YFM80RX Owner's Manual page 6

Your ATV was delivered with an adjustable speed limiter and also with an air intake restrictor plate. Yamaha
recommends that all beginners start off with the speed limiter screw turned in and the air intake restrictor
plate installed to limit the amount of speed available while they learn. The limiter screw may be gradually
turned out to increase maximum speed as the beginner becomes more familiar with operating the ATV. Par-
ents should decide when to adjust the ATV for more power as their youngster's riding skills improve. Once
the ATV rider can operate with skill at the top speed permitted by adjusting the speed limiter alone, the air
intake restrictor plate can be removed. Since removal of this plate will result in a significant increase in pow-
er, turn the speed limiter completely back in again; adjust it out in stages as you did before.
If your child is a beginner or is inexperienced, he or she should take a training course.