Tachometer problem

Discussion in 'The Garage' started by mas335, Mar 7, 2013.

  1. mas335

    mas335 xendurist

    Joined:
    Jun 17, 2006
    Oddometer:
    1,987
    Location:
    Piedmont region NC
    I have a 1988 Honda NX650 speedo/tach assembly that has worked fine until recently. The tach is electronic.

    When at idle it reads about 800-1000 rpms high, at road speeds ( 65-70mph ) the tach reads about 2,000-2,500 rpms too high. I have temporarily installed another NX speedo/tach assembly just to be satisfied that the problem is in this tach itself and it is, the substitute tach worked perfectly. Other than the hi rpm reading everything else works as it should but the screwed up tach reading is just not acceptable.

    I have owned 4 NX650's and worked on a few more plus many other Hondas of that era and this is the only problem of this kind that I have seen or heard of. Anyone else heard of this issue and is there a solution.

    Thanks,
    #1
  2. LuciferMutt

    LuciferMutt Rides slow bike slow

    Joined:
    Aug 19, 2008
    Oddometer:
    11,587
    Location:
    New(er) Mexico
    Have you had the instrument cluster circuit board out for any reason before this problem started? Some tachs have little dip switches on them for number of cylinders, etc. I have no experience with the NX650, but it might be possible a switch got moved?

    Where does the tach get the signal -- from the coil packs?
    #2
  3. mas335

    mas335 xendurist

    Joined:
    Jun 17, 2006
    Oddometer:
    1,987
    Location:
    Piedmont region NC

    Keep in mind that the tach worked perfect one day and the next time I fired it up this issue appeared.

    I did take it apart to clean the back side of the lenses but there is no such switch inside and not a "real" circuit board. The NX650 (single cylinder) does not share this tach configuration with any other model that I am aware of. Yes, it is wired in to the coil.

    The back up NX tach works perfectly but reads in KM which is just annoying.

    Thanks for the input.
    #3