Rear Sprocket Recomendation!

[briggsman]

Hello all, I am putting yt125cc 2stroke engine on my cart its a 5-speed manual with a 11 tooth sprocket all ready mounted on it. howmany tooth sprocket should i put on the axle, The bike the engine came off of had a 39 tooth axle sprocket but i dont know if that will work ok for the cart or not with the smaller tires. Im looking for good exceleration with a decent amount of top speed. Hope you guys can help!
thanks

 

[Jerryburger]

You'll need a fairly small tooth count on your rear sprocket because your kart wheels are so much smaller than the MC that it came off of. Compare the diameters of the MC wheel vs the kart wheel and use that to figure your rear sprocket.

Here's an example (REALLY GUESSING the tire sizes at this point.)

Old MC wheel dia. (inc. tire) 24"
New Kart wheel dia. (inc. tire) 12"

Divide the kart wheel by the old MC wheel size....... 12/24 =.5

Multiply your old MC sprocket by the answer from the above problem.... (39T x .5= 19 or 20T)

So, to approximate the acceleration/top speed of your old motorcycle, you'd run a 19 or 20T sprocket on the rear axle.... ASSuming that I'm anywhere near correct on the guesstimated tire sizes.

 

[briggsman]

Thanks for the help, ill do just that!