Early in my ownership of my '04 919, I put a 17T countersprocket on (mostly for the increased gas mileage). One of the benefits is that it goes a long ways to eliminate the stupid speedo offset. Recently I entered my subdivision and noticed the local gendarme had dropped one of those radar trailers on my route. You know, the ones that post the speed limit and give you an instant read of your speed. I drove by it about ten times over the next few days noticing my speedo reading and the trailers readout. between 10 and 30 mph it was right on.
Is this relationship linear so I can extrapolate that the error has disappeared all the way up the scale?
Has anyone else observed the healing effect of the 17T sprocket?
Yes, the 17t fixes the speedo. For proof, see www.919.org. Go to the mods page, and click on 17t sprocket. On the first page is a tab for an excel spreadsheet that will show you speeds in relation to sprocket selection.
Also, I had the 17t, and I checked speed with a GPS. Almost dead on, within 1mph either way throughout the curve.
While I have not had the opportuntiy to check the accuracy of my speedo, my previous Honda, an '88 NT650 Hawk, had an error of 15% on the speed, but the odometer was accurate to less than .2% (!) This was checked while traveling through Oregon and keeping track of my trip meter reading which was reset at the border. At mile marker 200, my trip read 200.3 and some. Has anybody checked their odometer instead of the speedo?
If it has already been done, it is safe to assume it is possible to do it.
On the other hand, if it has not been done never assume it is impossible to do it.
------- Rob --------
I can't answer your question specificaly but I can say that with a GPS on my bike that the speedo is always about 5mph low no matter what my speed is. So if the error is linear I would think that the fix would have to be linear also. There is nothing about that 17t sprocket that can be nonlinear.
a speedo inaccuracy should be proportional, so I totally agree with what CPG74 indicates.
My speedo is like WAAAAY off. I haven't counted the rear teeth yet, but the front seems to be a 15. I have an extra 15 in the box, which was supposed to be the "stock" front sprocket, but I'm the 3rd owner, so who knows...