Actualy Coopz, the more I think of it, changing the rear sprocket should not have anything to do with RPM and speedo readings as your bike should have the speedo drive comming off of the front sprocket bolt. The speedo reading is a funtion of engine speed and not ground speed.

One of the mods that the guys with the older models do is to go from a factory 43T to a later model 42T sprocket to reduce RPM. Those bikes have the speedo drive off the front wheel hub and there is not a direct connection between engine speed and indecated ground speed.

After talking with one owner of the older model, he told me that he reduced the engine spreed by 1000 RPM by installing the 42T sprocket.

 

Agree, the speedo reading vs. rpm will be the same but the actual speed vs. rpm will change.

 

R1000, I guess we should use theword mainshaft. The engine RPM would change going through the gears but the mainshaft dictates the speedo reading.

 

Agree, the main shaft dictates the speed-reading vs. rpm that will be absolutelythe same whatever front and rear sprocket is used.

However,the actual speed vs. engine rpm will change when the number of front or rear sprocket tooth ischanged. E.g. in case the front sprocket is changed from 17 to 16 teeth, the speed at a given rpm will be reduced by 17/16= 6.25 percent and the torque will increase by the same amount on all gears.

 

My '87 has a 42T rear sprocket and it pulls 3400rpm at 100km/h. I find the taller gearing makes for a more comfortable ride on open roads. This is more useful for me than being able to get 0-100km/h in 2.5 sec rather than 3.0sec.

 

My stock 91 turns 5000 RPMs at 75 MPH. in 6th gear.
If my math is correct 100 KPH is 62.5 MPH
so 4000 RPM at 62.5 MPH is pretty normal.
for these machines.

 

I've been pacified