[Trey_Quincy]

i have a 2002 with about 7100 miles on it. It is bone stock, except for turn signals a hotbodies undertail. i have been questioning the speedometer lately considering i am getting passed on the highway all the time. when i am going 55 mph i am running about 2700 rpms in 6th gear. I check with my garmin mobile gps on my cell phone the other night and to actually go 55 on the bike i had to go 63 to 64 on my gps. i checked the gps with my ford taurus and at 60 mph on the speedo, the gps read 60.1 so i know the gps is right on. i am running stock gears 16 front (i assume) and 40 on the back. The rear sprocket has 40 stamped on it. the guy i purchased it from says he never changed the sprockets. won't know about the front until i pull the plastics off i guess. also how much does rear tire wear affect the speedo. i have also included a pic of the rear tire. it is dunlop d208 190/50/17. i can't believe the factory would set the speedo 9mph off. that seems like a lot for 16/40 gearing. the RK chain i am running says 50 on it. i am assuming that is how many links or something. i am a noob to the rc51, but love the bike. need to change the oil (not looking forward to that since i don't have a rear stand.

i have been riding for a while. so i am not a complete noob.

1st bike. 1990 Honda VTR250 Interceptor. (best 250 bike ever built and
it was a vtwin)

2nd bike. 1987 Yamaha Radian 600

3rd bike. 1995 Kawasaki Ninja ZX6r

4th Bike. 2002 Honda RC51 (best superbike ever built)

 

[SubSailor]

If your rear sprocket is stock (40T), then he may have lowered the front by 1T down to 15T.
Also, depending on your speed, it's not uncommon for a speedo to be 6-10% off either.

 

[Trey_Quincy]

talked to local bike shop

when to my local bike shop and talked to their mechanic supervisor. first asked him if he had the knowledge to back up what he was going to tell me. He told me he has done all the Harley Davidson school certs, Suzuki and Honda. Guess he is what you would call a master mechanic or something, not much on all the certs and stuff.


he told me that 9mph off is possible with stock gearing. he has seen some harley vrods off 15 to 22 miles per hour from the factory.

speedohealer in my future i guess. anyone got a used one.

 

[Trey_Quincy]

found out today that i have a 15t sprocket on the front, called the original owner and he said he never changed it, but noticed that the mph were always off, could this just be a factory screw up. probably going to change the 15t to a 16t so my speedo is correct.

 

[RuZZeLL]

Speedohealer

$109 on eBay. Turns out the store is in Alhambra, CA which is a few minutes from me. The thing is super easy to install. Not I'm not racking up 17.9% more miles like before.


Hello by the way. The name's Russell. Been riding for several years, new to the forums, had a ZX-6, F4i, 'Busa, and now an RC51. LOVIN it.

See you guys around.

RuZZeLL

 

[SubSailor]

found out today that i have a 15t sprocket on the front, called the original owner and he said he never changed it, but noticed that the mph were always off, could this just be a factory screw up. probably going to change the 15t to a 16t so my speedo is correct.

Are you sure he's the original owner?
These bikes came with a 16T sprocket up front, and a 40T rear.
As such, they were over-geared.
Most RC51's are changed to a 15T front and 41 to 43T on rear for better performance.
Then a Speedo-Healer will show correct speed and mileage.

 

[DRFLGD]

found out today that i have a 15t sprocket on the front, called the original owner and he said he never changed it, but noticed that the mph were always off, could this just be a factory screw up. probably going to change the 15t to a 16t so my speedo is correct.

Sub Sailor is correct. Putting it back to stock gearing will not "heal" the speedo error. You will need to get a speedo healer or just deal with the error like many of us do.