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Discussion Starter · #1 ·
I forgot to ask also i dropped one tooth on the front and my feeble calcs show about 7 % change in ratio so is the top speed likely to be about 142mph now if theoretical 154 before(track showed 158 once on speedo) and my sppedo has started jumping from 69 to 92 at a steady 5k on the motor was it seemd of before but now is all over the place >?

Mike
 

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Hi, if I understand your post correctly, you are saying that our speedo is jumping around rather than increasing/decreasing smoothly ?

Changing the sprocket gearing will decrease your speed across all gears and result os higher reving to achieve the same cruise speed. It also gives the effect of increasing the power (or at least feeling like it does:) I did the same thing on my old Aprilia by adding 3 teeth the back sprocket because I wanted a quick take off more than a top speed of 250km/h :)

Changing the sprocket gearing will not effect your speedo. The speed works from pulses sent from a sensor mounted by the rear brakes. If it's jumping around then there's something else wrong. Possible the instrumentation unit itself.

ciao
Derek
 

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Discussion Starter · #3 ·
nearly..

Nearly i have 2 issues sorry i was not clear, one is my new top speed and i have lowered the gearing i know it will be less and did a basic calc (15 is one less tooth divided by the original 16 teeth is 6.25 % difference, say top speed was 154mph now it would be 6.25 % of 154mph so 144mph is this right or am i having a bad day again lol....

The other isssue is naughty speedo doing its own thing, i am going to check the rear wheel sender and wire and clean the contacts etc, i had heard that some speedos are prone to being crap!!! ?

thanks Mike
 
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