Re: Gear range or Cassette size for shifter kit
Let me add this to that, like I said I have a 13-34, 6 speed cassette, my 4th gear is almost exactly the same as running a 44t sprocket. In 4th gear I top out at about 34 mph and the engine is spinning pretty good. I can get 38 to 40 in 5th. When I shift in to 6th it now tops out at 35mph. So my point is that the engine only produces so much power and no matter how you gear it you won't go any faster. The only way to go faster is to increase horse power or decrease drag.
Let me ask this, have you seen how fast it goes in 4th gear? How fast in 5th gear? If your 4th gear actually gets you going faster than 5th then increasing your gearing won't get you anywhere. If 5th goes faster than 4th you might want to try a different cassette, which was already mentioned or try an 11 tooth jackshaft sprocket. That will increase you entire gearing. So your low gears won't be as low but your top gear will be taller.