NCY Secondary / Final Drive Gears for 125cc – 150cc GY6 Scooters, ATVs, and Go KartsFitting a big bore kit does not always give the expected increased top end speed, it certainly improves acceleration well but not top end speed, Why This often down the short gear ratios on your scooter, so if you find this is the case, the only way to combat this is by changing the gears to new longer ones.AVAILABLE: 14/3614/3714/3815/36 +7.2%15/37 +7.4%15/38 +7.6%16/36 +6.8%16/37 +6.9%16/38 +7.1%Please note: There are variants within the imported Chinese scooters so we would seriously recommend you remove the old gears and ensure count the number of teeth prior to purchase.**