you want speed or torque?
go faster could mean accelerate more quickly, which this thing will NOT do with a small sprocket.
go faster could mean have a higher top speed, which this thing will have, but it will take FOREVER to get there, and have crappy acceleration.
To be clear, faster does not equal more fun/excitement. Have you ever driven a stick shift car/truck? Try starting it in 4th gear and see how fun that is. You burn up your clutch, and it wont go, even though its "faster" too bad go karts like this dont have multiple gears, so you are left with
1) deal iwth it and burn out your clutch, and have a crappy driving experience unless you have long stretches to maintain your speed
2) regear to a lower speed and have acceptable accelleration.
either way, this go kart has been modified likely choppped the end off and put a chinese 4 wheeler rear end on it. Doesnt look safe. Way too high. Probably super loud with that tailpipe on it, and i personally would avoid it. In short
this thing will have no balls, tip over easily, burn the clutch up, and piss off all your neighbors because its really loud.