New rear sprocket

[Hayabusa-J.R.]

just changed my rear sprocket to a 43 from a 40 tooth,but the rpm's are in the same spot,what gives? is it because my speedo is off more now,and if so why is ever other sprocket topic say they are always higher in the rpm's when they change.

 

[ranman]

yes it is because your soeedo is off. you need a spedo healer.

 

[gsteve]

speedo is off stk... now its WAYYYYYY off. sj

 

[Tufbusa]

Your speedo is hooked directly to the front drive sprocket so it's not going to change your RPM to Speedo ratio no matter what sprocket you use on the rear. The Trick is to make the speedo on the dash match your accurate speed of the rear tire. That's where the speedo healer comes in handy.

Your speedo is not just about 8.5% faster than the bike. When your speedo is registering 108.5 MPH you are actually going 100 MPH. Buy yourself a speedo healer, plug it in, adjust it to minus 8.5% and you are on your way.

 

[Quasar]

Your speedo is hooked directly to the front drive sprocket so it's not going to change your RPM to Speedo ratio no matter what sprocket you use on the rear. The Trick is to make the speedo on the dash match your accurate speed of the rear tire. That's where the speedo healer comes in handy.

Tufbusa is exactly correct with respect as to why there is no offset in RPM with gearing changes of any kind.

If you are using 17/43 gearing, that's a 7.5% shorter gearing than stock gearing. In addition, ALL factory speedos have a factory speedo error (always reading higher than actual speed), and that ranges from 3% to 10% however, I find more are in the 5% area (my 99 Hayabusa's factory speedo error is 5.25%).

Therefore, when using a Speedo Healer or Yellowbox to correct your speedo, you need to correct by the factory speedo error as well as the actual shorter gearing. Your total correction factor would be 7.5% (your 17/43 gearing) + the factory speedo error (use a nominal 5% factory error) for a total correction factor of negative 12.5%.

 

[steelhead]

Surprised why a recall is not necessary for such an error.