Its not that much, but i have to tune differently were i live, i couldn't pull of a 50cc Setup with 15:40 Gearing, it would be impossible getting up hills Nicely, right now My 65cc Airsal Maxi has 12:45 Gearing and goes 35, up the hill that i ride up regularly (marked with 28%, Realisticaly about 22% over 100 Meters) wich i can get up at a little under 30mph, a Stock 2hp E50 Maxi can't even get up there at walking speed without having to pedal, so yes, i tune for Low end and Gear Short, no way i am going to go higher than stock gearing on an e50(13:45), Za50 or Z50 maybe, but probably not. (edited)