first of all, what size wheels does your bike have on it?
if you have 26" wheels and you are running a 44 tooth sprocket, you should be getting close to 30 mph top speeds with that set up.
if you drop to a 41 tooth you will see a TINY increase in top speed, but not very much.
if you drop to a 36 tooth sprocket, you will gain quite a bit of top speed, but you will lose a ton of bottom end torque for take off.
a smaller rear sprocket gives you more top speed, less low end torque and a lower crusing rpm .
a bigger rear sprocket will give you less top speed, more low end torque and a higher cruising rpm.
now, tire size has something to do with this as well because if you have a 26 inch rim with a 27 inch tall tire, it won't have as much top speed as if you had a 26 inch tall wheel with a 30 inch tall tire (for example).
the smaller the rear wheel and tire, the less top speed you will get.
for example, one of my bikes has a 20" rim with a 22" tall rear tire and a 41 tooth sprocket. my top speed is around 25 mph.
my other bike has a 20" wheel with a 24" tall rear tire, and a 41 tooth sprocket. top speed on that bike is around 32 mph.
both bikes have modified exhausts, re-jetted and tuned carbs, and they both weigh about the same.
sprocket size, wheel diamter and tire diameter all have a lot do do with the final gear ratio. you can change the gear ratio simply by putting on a taller or shorter back wheel and tire.
but always remember, a smaller rear sprocket will give you more top speed, lower crusing rpms, but you will lose bottom end torque. basically, it will take longer for you to get up to cruising speed and to top speed.
a bigger rear sprocket will give you more low end torque, but less top speed. you're bike will get up to cruising speed and top speed quicker (but your top speed will not be as fast as if you had a smaller sprocket.)
gear ratio numbers are backwards that what you would think. A higher number is actually a lower ratio, and a lower number is actually a higher ratio.
for example, lets say that we have a muscle car with a stock v-8 and we play with the gear ratio a little. lets assume that we change nothing on the car except for the gear ratio in the differential and we start with 4:88:1 gearing. this gearing would be low and good for quick acceleration used on the drag strip, gas mileage will suffer, the engine will be revving higher, and top speed will go down.
lets assume that this car will run the 1/4 mile with this gearing at 13.0 seconds at 90 mph (a 4:88:1 ring gear is physically bigger around than a 3:08:1 ring gear)
now lets take that same car and put3:08:1 gearing in it. This gearing is high, acceleration won't be as quick, gas mielage will go up, the engine rpms will be low, top speed will go up.
so now this car may run the 1/4 mile in 17.0 seconds, but the top speed may go up to 95mph.
with a lower gear (bigger physically) the car will accelerate faster and got to the end of the track in less time than if it has the higher 3:08:1 (smaller physically) gear. but the smaller gear gives you more top speed and less quickness on acceleration.
