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battery question

Discussion in 'Technical and Troubleshooting Torque' at netrider.net.au started by josh909, Jul 29, 2005.

  1. ok, so i go to walk out of work tonight, get to my bike and discover that for some god unknown reason i decided to leave the key in with the ignition on when i got back from lunch :?

    result: completely flat battery :|

    manage to roll start her and take off home. not before long i notice i have no indicators nor instrument lights - fair enough i think.

    then the VTR starts doing weird stuff - spluttering when i'm stopped at lights and backfiring :eek:

    i manage to get to MCAs on elizabeth where i turn her off and see if the battery has charged at all... nothing. i buy a new battery and trickle charger. throw the new battery on, just manage to turn her over and away i go - all seems fine, got all electrics going and she sounds sweeter than ever.

    now i'm at home with the battery on the charger :D

    my question is: was the spluttering/backfiring somehow due to having absolutely no charge in the battery? as i said she was fine once the new one was in and when i got home i turned her off and then tested if she would turn over (which she did). i know it definitely had nothing to do with fuel - i filled up 2 days ago and all has been fine.

    thanks in advance guys.
  2. If the electrical system was completely dead then it is quite possible that at idle the alternator was not providing enough power to both charge the system and generate a sufficient spark to keep the engine running smooth.
  3. so if your theory is right, does that mean that with the new battery (which is charging now) that this won't happen anymore?
  4. Yeah, if their is a full charge in the battery then this should be able to compensate for the drop in output from the alternator when the engine is at idle.
  5. As far as my knowledge goes No it won't happen anymore. Because the electrics were so dead the plugs may not have been producing a spark on every cycle. Therefore you end up with petrol/fumes in the exhaust which consequently go off in the hot exhaust. So having a good battery should stop the miss spark problem.

    I had a mate who completely BLEW UP his muffler on the car after seeing somone else do this. If your car is a Carby:

    1. Start the car and begin driving
    2. whilst moving (in a straight line) turn off the car
    3. pump your foot on the accelerator 5-7 times or hold it down for a few seconds
    4. start the car again.
    5. BOOM!!!!

    I'll see if i can find the pics of the muffler with a ripped open like a bombs gone off!!! :LOL: :LOL:
  6. thanks guys. the trickle charger has already gone into float mode and i have a bit of a ride tonight so i'll report back and let you know that all is cool (fingers crossed) ;)
  7. HaHa, my old Alfa Romeo used to do this itself (faulty ignition switch) which created a sharp "crack" that sounded exactly like a rifle shot. Did it to me once while pulling out of a carpark in front of a bank causing a nearby pedestrian to dive for the ground. Scared the daylights out of a cyclist once to - all unintentional but still funny (to me anyway).
  8. We used to do that in the main street of Wollongong on Saturday night just as we got level with some tatsy sorts on the footpath...had the same effect as taking a girl to a scary movie!!!
  9. Something the modern systems do to upset us.

    In the past a flat battery was treated by a push start. The smallest spark would fire the engine. Then the GENERATOR would start to charge the battery. Unfortunately generators take a few horsepower to work. SO, they came up with the alternator. It could produce much more power and used very little power from the engine.

    However, if the battery is real flat, the alternator will not charge.

    Generators have their own magnetis fields to produce the power. Alternators rewuire their fields to be exited by the battery. If battery is so flat it cannot exite the fields it cannot charge.

    You experienced the latter. Because there was a slight charge, enough to run coils, as soon as blinkers came on, no power for anything. Because blinkers are intermittent, spark is intermittent.

    Your new, or charged battery will fix all the problems.
    Still might pay to get a voltmeter on the battery while running, should be in vicinity of 14v as said by someone earlier.

    Good luck with it.

  10. Yup, all above is correct. (Including the "Key Poppers" - exploding exhaust trick - Just a note on that one, it only works with manuals as far as i know, and you have to leave it in gear with the foot off the clutch when you do it)

    Alternaters usually wont charge below around 1000rpm, so that would explain the rough idling at lights, with no battery to take up the slack.
  11. ok, just back from a quick ride up to berowra and all is fine... thanks for the replies guys :D