This is a Guide for figuring out your final drive ratio, as well as speed.

This formula might not be the simplest way to do it, but it's one that works.
Grab a pencil and some paper... you'll need it.

Ok here we go.

The formula works in 5 parts.
 
Part (1) 
Take the number of Teeth you have on the clutch for the motor, and divide that by the number of teeth you have on your rear sprocket.
EG: So if you have 10 teeth on the motor side (Or Clutch) and 52 teeth on the rear sprocket, you do this: 10 divided by 52, ( Not 52 divided by 10)
The number you should get is 0.19230 then a whole bunch more numbers after that, just use the first 5 after the (.), Ok write that number down.
 
Part (2)
Then take your max RPM (3600 in this case) and times (x) it by 60, you should get (216000) write that number down.
That is your (RPH) Revolutions per Hour)
 
Part (3)
Now you need to figure out your tire  circumference, Take the tire height In inches and times (x) it by 3.14
EG: a 22 inch tall tire has a Circumference of  69.08 write that number down.
 
Part (4)
Now take 63360 and divide that by your tire circumference, write that number down,  (907.73638)
(63360 is how many inches are in a mile) (IPM) Inches Per Mile
 
 
Now we figure out the answer, (MPH)

Part (5) 
Take the answer in part one, and times (x) it by the answer in part two ( Ratio times (x) RPH ), take that answer and divide it by the answer you got for (IPM) 45.7585 etc etc
So if the Kart (or Bike) can get to 3600 RPM under load then the kart (or Bike) with the gearing as it is, will go 45.75 MPH

If you are using a Jackshaft simply take the MPH and divide it by the Jackshaft ratio
EG: take 45.75 and divide it by 2 (2 for a 2:1 Jackshaft) you should get  22.875 MPH
 
Yeah it takes a little getting used to, but it works and is correct.

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