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Reversed polarity when connecting new battery

Discussion in 'The Garage' started by Houghton, Aug 13, 2022.

  1. Houghton

    Houghton XS400 Member

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    I bought a YB12A-B battery for my '79 XS400 2A2 and hadn't realised the significance of the B at the end. It means the polarity is the opposite of the more common A version. Anyway, I connected it as I normally do and the bike wouldn't start. I realised my mistake and consulted the Haynes manual which states the 'electrical system will be damaged permanently'. I bought the correct battery, and found the lights etc and fuses all ok. However, starting is difficult (only the electric starter works) and when it does start the engine cuts out after a few seconds. Previous posts refer to solenoid and regulator damage, and I wonder if the Piranha electronic ignition pack I fitted in 1982 could also have been damaged. Or is the Haynes manual correct? Any ideas?
     
  2. Kitchi

    Kitchi XS400 Enthusiast

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    If your bike has a TCI box it might be toast. The regulator might have suffered damage also. Electronics do not like to be connected in the reverse polarity.
    I cant see the starter solenoid being damaged it is just basically a coil of wire. If it has a separate rectifier from the regulator The rectifier should be fine. I know you said the fuses are good but i would double check the ignition fuse with a meter or even replace it completely. In some cases (not often but it happens) a fuse does blow but it looks good.
    Sometimes manufactures design a circuit to blow a fuse when hooked up back wards instead of cooking a modal.But don't count on it.
     
  3. Houghton

    Houghton XS400 Member

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    Many thanks. Are you saying the electronic ignition is kaput or the bike itself? I saw a NewTronic pack is available at yambits, though it costs five times as much as I paid for the Piranha unit in '82. The original points set up was useless.
    How do you account for the fact that the bike actually starts, albeit for a few seconds only?
    My neighbour is a great bike enthusiast and knows a very competent local mechanic. We're taking the bike to him soon. I'll check all the fuses anyway.
    Cheers.
     
  4. Kitchi

    Kitchi XS400 Enthusiast

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    I said it might be toast. all you need is 3 things for your bike to run.
    1. fuel and air mixture
    2. compression
    3. spark at the right time
    If it ran before the battery was connected in the reverse polarity I would say it is an electronics problem is causing the issue.
    If it starts and then dies compression should be ok.
    The carbs don't care about polarity.
    So the only thing left is the electronics

    You could try to unplug your regulator just in case it is doing something funky when the bike is running that is causing it to stop running and then start your bike to see if there is a difference.

    This all assumes that the bike was running correctly.
     
  5. Houghton

    Houghton XS400 Member

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    Yes, agreed. It must be electrical. It was running OK before, though I hadn't fired it up for 9 months. At least I can point the workshop in the right direction, and the main electrical/electronic components still seem to be available, which ain't bad for a 44-year-old bike.
     
  6. Kitchi

    Kitchi XS400 Enthusiast

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    Just a thought before you start buying replacement electronics unplug the regulator and try to see if the bike will run without the charging system.
    If you are lucky the aftermarket ignition system that was installed may have an over voltage protection built in and the regulator is not regulating properly.
    if it runs good after the regulator is unplugged all you might need is a regulator.

    Regulators I am sure Mikes XS has them. replacement TCI units are available on Ebay(used). I don't know if aftermarket ones are available.
     
  7. Houghton

    Houghton XS400 Member

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    Many thanks, again. I'll report back on what happens. Seems the mechanic is on his hols at the moment, so maybe a while before anything happens.
     
  8. Houghton

    Houghton XS400 Member

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    UPDATE 9th Sept.....
    I arranged with my neigbour to transport the bike on his trailer to a local bike enthusiast who sorted out his old BSA a few years ago...lives very near, which helps. Anyway, had yet another go at starting it....30 secs on the starter without success, and then it fired up on the first kick!...and the engine kept running. The rest of today it's started on the first kick, and it seems to run OK, 'cept for the rear brakes (yet again). We'll see what happens tomorrow. To think I spent at least an hour kicking & bumping it a few years ago, when the battery 'problem' occurred, and 30 mins the other week. The only thing I did today was switch round all the fuses, replacing the missing headlight one and changing the ignition one. None were blown as far as I could see. Your advice could well have worked - thanks! I'll certainly have more faith in people like you & the XS forum than Haynes manuals in future.
     

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