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Thread: Need to calibrate my spedo on a 85 K100

  1. #1

    Need to calibrate my spedo on a 85 K100

    I would like to calibrate my spedo using a signal generator before I put it back in the gauge cluster. Is this possible? If it is can anyone tell me which hole is for what? I have a list of the frequency for each speed from the forum so I know what the values should be. I also have an oscilloscope so i can generate any kind of wave I need and adjust the duration of the pulse. Is there any particular type of wave I need to generate? I.E. Square wave, Sine wave etc.?

    I found these values on another site, they are for a K1100. Are these values the same for my 85 K100

    Speed, MPH Frequency, Hz
    10 13.33
    20 26.67
    30 40.00
    40 53.33
    45 60.00
    50 66.67
    55 73.33
    60 80.00
    70 93.33
    80 106.67
    90 120.00
    100 133.33
    110 146.67
    120 160.00
    140 186.67
    150 200.00

  2. #2
    Registered User
    Join Date
    Apr 2005
    Rapid City South Dakota

    Adjust Speedo

    From the data you have listed 45 miles/hour equals 60 cycles/sec. That frequency is generated by a pistol soldering iron. Pull the sensor out of the final drive and hold the soldering iron near it and you should find out how for off your speedo is at 45 m/h. The two links should be helpful and the second link has a link to a picture of the adjusting pot. The third link went way over my head but may be helpful to you. I simply took my speedo off a whole bunch of times till I got the speedo near my sigma bike computer. Good luck Harold in Kansas
    Harold In Rapid City, SD
    1985 K100RT Bullit
    1985 K100XX/EML Bemel

  3. #3
    wow that seems like it was a real pain. I have been talking with my dad who worked at 3M in micro electronic R&D so I am hoping he can help me make a test rig to get this done with out removing it many many times. I think we are going to try a signal generator and a power supply and see what that yields. I will post the results if it works and if it does not hide and never visit this thread again. JK

  4. #4
    Registered User 58058D's Avatar
    Join Date
    Jun 2007
    Mendocino, CA USA about as far left as you can get in the lower 48
    Back when these were our 'new' rides, many of us just stuck on a bicycle computer and used that if we wanted reasonably accurate velocities. Much cheaper and easy to do. Some of us also did this temporarily to chart the 'true' velocity and then made appropriate marks on the speedo for reference - or just remembered what 45 on the speedo meant (usually 40 in real life). The disparity was not usually linear, or at least was not for my '85 RS. But, my local CHP helped me to understand the relationship a couple of times......
    Jim Douglas '00 K1200RS >138,000 miles -- Black, 01/10/2000 to present
    Gone: White '09 K1300S sold @ 22k mi, Black '93 K1100RS traded @ 78k mi, Red '85 K100RS sold @ 44k mi, '06 Kaw 650R chrome yellow track bike sold

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