Stingray with a 4 stroke looking for recommendations

[dmopedMA]

Related to this topic:
https://motoredbikes.com/threads/pr...chopper-and-im-looking-for-some-advice.50872/

I would like to know which will be the right sprocket to put on a 20 inch back wheel, I'm planning on a 49cc 4G from bicycle-engines and the default sprocket coming with the kit is 48 tooth and I feel it too big, they offer transmission pulley in two sizes: 80 and 100 tooth, no idea which one to choose.
I'm looking for not having to pedal at all and I don't need more speed than 25-30mph on flat.

 

[CrazyDan]

Get the one with the 80 tooth pulley, use the 10 tooth output sprocket and get a 40 tooth rear sprocket. 16:1 gear ratio on a 20" tire will pull hills and do 26 mph.
Edit: pretty sure 20" isn't the correct number to use in the equation, how tall is the entire wheel and tire inflated? I'm guessing maybe 24" so you might wanna keep the stock 48 tooth rear sprocket with the 10 tooth output sprocket and it'll maintain roughly the same wheel torque and 26 mph top speed on a 24" tire with a 19.2:1 reduction.