Hi guys. I ride a Busa and the speedo/revs pickup is at the front sprocket. My original gearing is 18/43. I have now changed that to 19/42 for these reasons...
A friend i was riding with to scotland was on an identical bike except that he was carrying a pillion, plus the guy was abou 4 stone heavier than me, BUT at the pumps we always put the same quantity of fuel in.....reason.....he had a smaller rear sprocket.
The other reason was that the speedo corrected itself.....first with the 18 to 19 tooth to 3% and then with the 43 to 42 tooth to exact.
I picked this combination because it was within tolerance of the chain length......be careful that you are within these tolerances or it will mean a new chain too, (might need one anyway?)
Riding it now is a little different. Needs a little revs to get going...before you could start moving off the clutch. Fast starts are less unnerving....wheelies more sedate and controllable.
Downside is that i need to use more gears now. I used to be able to pull from 20mph in 6th.....now thats more like 4th.
Just do it matey. If you dont like it, you can always put it back