Unlock the full potential of your QMB139 50cc 4-stroke scooter engine with the NCY Performance Gear Set
This kit is made specifically for larger big bored engines and increases your gear ratio by 26%. This will allow you to maximize your big bore kit by increased top speed and a more usable rev range. You won't see much if any improved performance if you install these on a stock top end. For experienced tuners only.
