Yamaha Zuma 125
Trailtech tachometer
$ 55.99
The TTO tach is a great, and cheap tool to help you tune your bike. No wiring necessary. Peel, stick, and wrap the wire around your spark plug wire. This will help the four stroke guys from over-revving, and help the two stroke guys know where their powerband is. The tach also helps transmission tuning.
Handlebar mount for 7/8" HERE