Got a 10T drive sprocket and a 44T driven sprocket (4.4:1) ratio. Want to change ratio to increase top speed. Would I be better off changing the drive or driven sprocket? Got a 100cc engine with 26" tires (but im sure the engine is more like 80cc.)
If I was to get a 40T driven sprocket would I expect a ~10% increase in max speed? And ~15% with 38T?
Since I just happen to have my calculator handy for another thread we can look at a few combinations to give you an idea of what kind of speed increase you would be looking at.
First we need to establish your maximum RPM. I am just going to use 6000rpm as a baseline since it is likely the most realistic, unless you have done some port work.
With your current setup, your top speed at 6000rpm is 25.7mph, give or take a bit.
With a 40 tooth sprocket that top speed at 6000rpm is now 28.3mph,
With a 38 tooth your top speed at 6000rpm is now 29.8mph
And with a 36 tooth sprocket, your top speed at 6000rpm is 31.4
Basically, in really rough numbers, every 1 tooth of back sprocket gives you roughly .75-.8mph at 6000rpm.
Here is the real kicker. A little port work to the cylinder to increase the powerband even 1000rpm will make a greater difference in top speed potential. If your engine could now top out at 7000rpm the top speed of the bike would be 30mph with the 44 tooth sprocket which matches the 38 tooth at 6000rpm, but would have better torque.