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81 GSX 750 Batt Flattery

Discussion in 'Bling and Appearance' started by 81gsx750, Feb 20, 2008.

  1. I'm no slouch when it comes to electrocaties...but the battery keeps going flat
    Ive replaced the voltage regulator with a honda job....(with the spare wire that links to the lighting circut)
    Getting voltage off all three phases and 13.8 volts at 3500rpm....
    Been keeping on top of the problem with a good old battery charger every 3 days
    This ones had me stumped for months now can anyone help???
    Also looking for a Right hand side cover plate badge (like the one in my profile pic)

    She's a lovley old girl and my daily ride, who ever owned her before my did all the right things...
    Intake cam grind
    Port polish
    Four into Ones
    Marzochi Rear shocks
  2. Sounds like either your battery's dead and failing to hold charge, or there's something draining juice when the bike's standing.

    The 13.8V suggests that the Honda rec/reg is doing its stuff. Have you done a rising volt test? (Checking that the voltage across the battery jumps up as the revs rise above tickover).

    When I fitted a Honda (CB250/400N) rec/reg to my own GSX years ago, I didn't hook the spare wire to anything. Still seemed to work OK :grin: .

    Have you an alarm/immobiliser/clock or anything else that exerts a permanent drain on the battery? It might be worth putting a sensitive ammeter in one of the battery leads with the bike "off" to see what's happening.

    But with a battery of unknown vintage or history, a new one would be the first place I'd spend money. If the bike has popped a rec/reg in the past, the battery may have been boiled dry and there's only a limited number of times they'll survive that :grin: .
  3. How often do you ride and how old is the battery are the important questions.

    "Wet" style batteries tend to last about 1 year, if you only ride once a week or once ever two weeks, before that start giving trouble.

    Then they will respond as you describe. If you ride a bit more often you will get a few years, but that's about it. Bike batteries are quite small for the work they do.

    If this is the case, then replace it with a "sealed" type. They don't mind being left sitting around as much and they crank harder for a given rating.

    If the battery is relatively new, then I would be looking for an electrical leak. Wires in older harnesses tend to crack. Given the age of the bike I wouldn't rule this out.
  4. Battery brand new

    Its a new Battery 3 weeks ago....
    I ride the bike every day....
    The ammeter sound like a good test to start with...that and a few more hours
    with a mutimeter in hand
  5. For your badges try Badge Replicas Australia.

    Sorry I can't post a link yet. Just Google it.

    I got a pair for my Geep and they are superb.
  6. Re: Battery brand new

    Just verify using the 10A scale and the meter in series with the + lead (you have to disconnect it from the battery first) that there is current flow with the key off.

    It is quite possible to have a faulty new battery. That must be the problem if there is no current flow when testing with the meter.

    If you do have current flow disconnect the new regulator first and check again. Remove fuses one at a time to see which circuit has the drain, and so on.


    Trevor G