Bikewithamotor, what is the diameter of your 24 tooth sprocket?
Here's a question... How much do you weigh??
If your real skinny like Baird (130 lbs), you can run something small like a 30T.
.
Baird is running 24" wheels which makes a difference of over 3 MPH at 7000 RPM
and
his motor is hotted up and much faster than stock....
Stock motor with 26" wheels should not go lower than 35/ 36 teeth on fairly flat ground
Go bigger if you are heavy and have a lot of hills
Altitude will decrease your performance too
24 tooth sprocket will give you a top speed of 55 MPH at 7000 RPM
which your engine will never pull