speedmeter and sprocket change

[kawashima]

When I had CB400SF, I changed sprocket and then speedmeter went wrong. That bike took speed from front sprocket.
Was there any method to adjust speedmeter?
I changed to smaller rear sprocket and meter indicated 90km/h when the bike was running at 100km/h.

[the grim reaper]

If your bike reads the road speed from the sprocket, there's no way you can change the gearing without introducing an error into the speedo reading. What you can do is to fit an electronic speedo by a company called 'Sigma', these are intended for bicycles but are handy because they go up to 99mph and work on a magnet on the front wheel. You measure the circumference of your wheel and programme the computer accordingly.

Apart from that, you could always work out the change in the gearing and put little stickers on your speedo to remind you of your actual speed.

To do this, work out the existing gearing and then do the same to the new gearing (i.e 12/42 to 12/40) and multiply it by the speed to work out the error.

Cheers

Grim
____________________
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[kawashima]

Thanks! Former one seems difficult, I'll try latter one next time.
(oh I need to check my bike now.)