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Thread: 84 R80 gs tach issue

  1. #1
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    84 R80 gs tach issue

    My gs has a tack that wont read past 4,ooo rpm. When wound past that still reads 4 grand. I got the tack from BMW when they were available so it was knew. Took it back as I thought it was the problem. Well same issue. Has to be in the bike, but what.

  2. #2
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    Quote Originally Posted by dougjordan View Post
    My gs has a tack that wont read past 4,ooo rpm. When wound past that still reads 4 grand. I got the tack from BMW when they were available so it was knew. Took it back as I thought it was the problem. Well same issue. Has to be in the bike, but what.
    No one every see this problem? I had the opportunity to meet Oak, stumped him to. I will live with it or take it off.

  3. #3
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    Well, your tach is an electronic device and it operates by the rate of field coil collapses of the ignition coil. That information is interpreted by the electronics in the tach. Snowbum has pretty nerdy discussion about the tach here:

    https://bmwmotorcycletech.info/tach.htm

    Since your situation suggests that it is the bike, I would get a wiring diagram and trace the signal from the coil to the block connector at the back of the speedo pod. Likely you have some corrosion or a grounding issue somewhere. That block connector can get corrosion on the pins and if they don't make a good connection to the speedo, then it could be a problem.

    I updated your thread title for better visibility and searching in the future.
    Kurt -- Forum Liaison ---> Resources and Links Thread <---
    '78 R100/7 & '69 R69S & '52 R25/2
    mine-ineye-deatheah-pielayah-jooa-kalayus. oolah-minane-hay-meeriah-kal-oyus-algay-a-thaykin', buddy!

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