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Tach going nuts and rough idle

Discussion in 'XJ Technical Chat' started by ericstanicki, Aug 9, 2008.

  1. ericstanicki

    ericstanicki New Member

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    new to the forum... YAY for me.... just bought a 82 maxim 750 and so far have had nothing but problems.... yeah yeah yeah its just my hazing.... anyways had a few issues with the charging system and replaced the regulator and stator but after cleaning up the splices and wiring im getting 14 volts. but now when i ride around and put a load on the engine its missing on one of the cylinders and i dont know if its related but when i rev the engine the rpms actually drop according to the gauge (not according to the jeweles!) so are they related and any suggestions.... Also if anyone is interested i now have 2 extra regs id get rid of for pretty cheap they all test fine and the diodes are intact.. Thanks again!
     
    ericstanicki, Aug 9, 2008
    #1
  2. MiCarl

    MiCarl Active Member

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    Your tachometer is electronic. It takes it's signal from the lead to one of the coils (I don't remember which one right off the top of my head).

    Probably you are having a spark problem (before the coil) and it's showing in the tach also.

    Interestingly, I had a similar problem on my Venture this morning. When the RPMs got up to 2K it would start to miss and the tachometer would drop to 0. Back off the throttle and everything would come back into place - until I hit 2K RPM again. The "jewels" and speedometer told me I was going beyond 2k, but it ran like crap.

    I had just washed the bike. After idling at a RR crossing waiting for a train the problem went away.

    My best guess is that I got some moisture in one of the connectors to the coil that happens to be on line with the tach. At 2K rpm is when the alternator starts to produce, and the extra voltage was enough to arc through the moisture to ground. No power for the coil and no signal for the tach.

    I wonder if fixing your charging system boosted your voltage enough to discover a "leak" in the ignition wiring.

    You can do a quick test by unplugging your voltage regulator. If the missing goes away and the tach straightens out then you know what to look for. Don't try to run very long with the voltage regulator unplugged, your battery will be dead in a few minutes.
     
    MiCarl, Aug 9, 2008
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