Author Topic: speedo error check  (Read 7772 times)

Offline rsexauer

  • Motobrick Curious
  • Posts: 13
speedo error check
« on: June 22, 2014, 06:52:31 PM »
This is my first post, had my 88 K100 for about 500 miles now and loving it. Where have you been all my life?
From what I have been reading excessive speedo error appears to be the norm. My experience as best that I recall is that on my bike I am turning about 4000 rpm's and the speedo is showing 70 mph and I am being passed on a regular basis. Is there an expected mph reading at a given rpm that I can compare to? I realize that engine tune may affect the accuracy but on a comparable bike with the same final drive ratio as mine I would expect similar mph/rpm ratio.

Offline wmax351

  • ^ Quintessential Motobricker
  • Posts: 1237
Re: speedo error check
« Reply #1 on: June 22, 2014, 07:21:44 PM »
This is my first post, had my 88 K100 for about 500 miles now and loving it. Where have you been all my life?
From what I have been reading excessive speedo error appears to be the norm. My experience as best that I recall is that on my bike I am turning about 4000 rpm's and the speedo is showing 70 mph and I am being passed on a regular basis. Is there an expected mph reading at a given rpm that I can compare to? I realize that engine tune may affect the accuracy but on a comparable bike with the same final drive ratio as mine I would expect similar mph/rpm ratio.


First of all, don't ride/drive at the speed limit, ride at what traffic is going. It's much safer.


In general, it is exactly 10% fast. 80mph indicated is 72 mph actual. It depends on your bike's setup/FD ratio, but with a 3.2:1 final drive on a K75, 6000rpm is 80mph actual.


There is an app, Karamba, somewhere here or on flyingbrick.de you can use to calibrate.
  • Albuquerque, NM
  • 91 BMW K75 Standard, 98 Moto Guzzi California EV
Bikes:
Current:1991 BMW K75 Standard, 1998 Moto Guzzi California EV11
Past: '83 BMW R65LS, '75 Honda CB550F, '69 Honda CB175, 1999 Royal Enfield Bullet 500, 1973 Triumph Tiger TR7V, 1971 BMW R75/5 in Toaster outfit, 1979 Harley Davidson XLS-1000 Sportster Roadster

Offline rsexauer

  • Motobrick Curious
  • Posts: 13
Re: speedo error check
« Reply #2 on: June 23, 2014, 05:27:06 AM »
I believe my FD ratio is 2.91:1, I was hoping someone with the same set-up would know the error corection value to see if mine was off enough to get into troubleshooting and correction if needed.

Offline wmax351

  • ^ Quintessential Motobricker
  • Posts: 1237
Re: speedo error check
« Reply #3 on: June 23, 2014, 03:32:19 PM »
I believe my FD ratio is 2.91:1, I was hoping someone with the same set-up would know the error corection value to see if mine was off enough to get into troubleshooting and correction if needed.


I'd put money that it is off. They are specifically calibrated like that from the factory, so far as I can tell. I guess that way they never show slower than actual, even with larger tires.


http://www.largiader.com/articles/gearing/


If you have the gauges off anyways, then is the time to adjust it. You can replace the lights with LED's too.
  • Albuquerque, NM
  • 91 BMW K75 Standard, 98 Moto Guzzi California EV
Bikes:
Current:1991 BMW K75 Standard, 1998 Moto Guzzi California EV11
Past: '83 BMW R65LS, '75 Honda CB550F, '69 Honda CB175, 1999 Royal Enfield Bullet 500, 1973 Triumph Tiger TR7V, 1971 BMW R75/5 in Toaster outfit, 1979 Harley Davidson XLS-1000 Sportster Roadster

Offline rbm

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  • Regards, Robert
Toronto, Ontario

1987 K75 - Build Blog @http://k75retro.blogspot.ca/

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