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How to calibrate the GPR-S speedometer

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Richard230:
I have discovered that the GPR-S main speedometer (not the CA) can be adjusted for accuracy by the owner. My speedometer was reading about 15 or 20% fast according to the two electronic speed check signs that are on my commute route of travel. Also, the trip meter and odometer were reading about 10% more miles than I had actually driven, based upon the mileage reading of my other motorcycles and my car's odometer. I wanted to fix this discrepancy.

It turns out that the speedometer has a small white plastic button located under the instrument panel. If you press this button and hold it, a four digit number will show. This number corresponds to a ratio of the wheel revolutions compared with time as interpreted by the speedometer computer. In my case the number was "1995". After some experimentation, I found that setting the number to 1760 by pressing first the left button on the dash to select a digit, then pressing the right button to change it, would cause the odometer and trip meter to read more accurately and would also lower the speed shown on the display to a mile or two faster than the actual speed of the motorcycle. I was not able to obtain both a completely accurate speed and also an accurate distance traveled, so I went for the correct distance and anyway a slightly fast speed indication is typical of most motorcycles. You can play with this number to achieve the level of accuracy that you want your speedometer to display.

If you push the left button after the last digit, you will get the gas fuel gauge, which you can set to "on" or "off". Obviously, this setting should be off. If you press the left button again, you get a series of "0"s and then some digits. This is the odometer reading, which can be changed to anything that you want, using first the left button and then the right button.  :confused:  Changing the odometer reading is probably illegal and I recommend that you keep pressing the left button until the time shows. The press it again and you will have exited the programming system.

Richard230:
Today I finally got a completely clear speedometer reading while riding home. The speed check sign read 38 mph, while my speedometer read 40 mph. The trip odometer is now exactly correct, within its one-tenth of a mile accuracy display. This is with a calibration setting of 1760, so it appears that my speedometer now reads about 5% fast, which is OK with me. That matches the accuracy of most of my other motorcycles, except for my BMWs, which tend to read about 8% too fast. Changing the calibration setting to 1670 would likely make the speedometer completely accurate if my calculations are correct, but I think I will leave things alone.

I might add that there is no guarantee that your GPR-S speedometer will have the same accuracy as mine. Who knows what the accuracy variation range is in these instruments? So anyone wanting to calibrate their GPR-S speedometer should set the reading around 1750 and verify the actual speed and distance by whatever method that you feel comfortable with.

skadamo:
Great information, thanks for posting! Do you know the manufacturer of the speedometer?

Richard230:
My understanding is that the motorcycle's main speedometer (the Cycle Analyst which is installed by EMS above and ahead of the main speedometer also has an integral speedometer function) is the one that is used on the Tiger Boxer 250. It does not have any brand markings on the instrument that I can locate. My guess is that it is probably made by Tiger or another firm in Thailand. It appears to be a simple device that counts the revolutions of the front wheel with a sensor, similar to a bicycle speedometer, except that it has a gas gauge display that can be turned on and off by cycling through the programming display.

Harlan:
Its the same speedometer that is on the Sachs bikes, which makes sense since the same factory builds the chassis for EMS.

Recognize this Sachs bike skadamo?


Hint:
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