Quote:
Originally Posted by kazam58
Any setup that has a front sprocket with more teeth than stock and a rear sprocket with less teeth than stock will offer better fuel mileage. If your bike has the power to pull then this will also give you a higher top speed (and less acceleration), so you can only change the gearing so much.
So the closer the ratio between the front and rear sprocket is 1:1 then the better mileage and top speed the bike will have. And vice versa.
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Neither of these statements are true. The only thing that is guaranteed with a sprocket swap for one with a taller gear (larger front and/or smaller rear) is that for a given road speed, engine revs will be lower.
At that same given road speed, the bike needs to produce the exact same thrust at the rear wheel (often measured as rear-wheel horsepower). If the engine is turning less revs, that often means the rider must use more throttle at that lower engine speed. Whether or not using more throttle at a lower engine speed uses more or less fuel than a higher engine speed with less throttle, well, the answer is it depends. And in many cases, there is actually very little difference at the end (for all reasonable changes in gearing). Depends on the particular engine's power curve, and fuel usage along that power curve. There's no free lunch. To push a certain bike a certain speed through the air takes a fixed amount of horsepower.
As for a taller gear ratio allowing a higher top speed, that's also B.S. for almost all production motorcycles. The only way that would be true is if the motorcycle could pull to the engine redline in top gear, so a taller gear ratio would allow the bike to go faster at the same redline. The ninjette can't pull to redline in top gear, so the point is moot. And any sportbike on the market today is geared such that it can't redline in top gear either; even the hyperbikes are hitting their 186 mph limiter at significantly below their engine's redlines.