/2 Conversion Thread

Discussion in 'Airheads' started by matteo, Sep 22, 2010.

  1. deafanddiabetic

    deafanddiabetic What? Huh?

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    Is there a way to test your rear brake switch for functionality?

    Red/Green stripe wire goes up to the ignition board (I don't have a front brake switch so it's not connected to the red/green there, it's going straight to the board) and the black/green is going to the tail light itself.

    My tail light is illuminated with insertion of the key, but depressed my brake pedal and moving the pin does not make my tail light bulb brighter. It's a dual filament bulb, it's got brown for ground, grey/white and black/green, I've tried swapping spots in the /2 bulb holder but it doesn't make a difference. Wondering if my fault is actually in the switch itself.
  2. Jim K in PA

    Jim K in PA Long timer

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    A simple continuity test across the switch terminals will confirm its functional. I would check continuity of the black/green wire from the switch to the bulb holder as well. grey/white is your tail light, so if that's lit, it and the ground leg are good.

    You could also just jumper the terminals with a piece of wire and see if it lights up. Assuming the bulb is good, of course.
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  3. budsboy

    budsboy Where it started

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    Be sure to check the ground connection.
  4. deafanddiabetic

    deafanddiabetic What? Huh?

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    Well, I left the key in the ignition overnight.

    IMG_2616.JPG

    Came back to this today. The ground totally melted through the coil, thankfully that's the only thing that took damage.

    Would this be caused by a bad ground? It could be a short but otherwise things have been working for several days.
  5. eldomike

    eldomike Who Cares

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    Points were closed....lucky it didn't burn up
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  6. bpeckm

    bpeckm Grin!

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    Yikes....:fpalm

    The /2 and /5 switches are, by today's standards, a little idiosyncratic: push the key down and ignition is ON, then turn to the left and right to activate headlight/parking light.
  7. deafanddiabetic

    deafanddiabetic What? Huh?

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    I'm an idiot for leaving it in, I knew it was live but just made a mistake. Now I'm a little worried to pull the front cover and see if anything got hurt in there o_O
  8. eldomike

    eldomike Who Cares

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    Typically will just overheat the coil...
  9. Jim K in PA

    Jim K in PA Long timer

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    And kill your battery. Ya got lucky on this one.
  10. lucky6600

    lucky6600 Long timer

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    It's always nice to have my name mentioned couple times when the situation like this happened.
  11. deafanddiabetic

    deafanddiabetic What? Huh?

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    Electronics are not my strong suit, can anybody explain why it would burn up the coil exactly? Like, if you left the key in your ignition on your car, it wouldn't have the same effect. Someone mentioned the points being closed, which of course makes a full circuit. Why would that concentrate on the ground of the coil and not just slowly drain the battery instead? Or adversely, what would be different if the engine was running, wouldn't it not produce the same (if not more?) heat and power in the circuit?
  12. Jim K in PA

    Jim K in PA Long timer

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    [​IMG]
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  13. bpeckm

    bpeckm Grin!

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    The difference with your car: with the key/nail IN on the /2 it is exactly as if you left the key in the ON position in your car. Back in the day when cars had points (nowadays they all have electronic this that and everything else!) the same thing could have happened if you had left the key ON. When running, the points are opening and closing constantly, so the coil is activated and the spark happens when the field collapses in the coil. It is designed to do that, and not to have a constant through-current as when ignition is ON, points are closed, and it just sits there draining the battery....
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  14. Geezerrv

    Geezerrv Been here awhile

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    Resistance creates heat so maybe that wasn't a really good ground?
  15. deafanddiabetic

    deafanddiabetic What? Huh?

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    When I get this melted rubbery mess fixed I think I'm going to add in a few more grounds to be safe. Can't go wrong with more grounds.
  16. Jim K in PA

    Jim K in PA Long timer

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    More grounds will have no effect on what happened. You clearly had a very good ground, hence the heat. I posted the diagram which shows the very simple circuit you are dealing with. The coil is a big resistor. The points is the switch on the ground side. The coil is full of oil to keep it cool, so the heat built up in the conductor on the ground side.
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  17. Geezerrv

    Geezerrv Been here awhile

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    I like Jims explanation best. I often see melted electrics where a resistance at ground is involved was my thinking.
  18. danedg

    danedg Horizontally Opposed

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    There is nothing "electronical" about this. This is basic automotive "electrics".
    Your battery found a "path" to ground, and couldn't "drain"... and you burnt up everything in the circuit.
  19. chasbmw

    chasbmw Long timer

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    Mine and other /2s don't have fuzes, so would one on the battery + lead, prevent this happening?
    Guess that with 6v need to be a low amperage fuze?


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  20. chasbmw

    chasbmw Long timer

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    This a a lovely looking bike, I think that is a combo of the biggish tank shape, together with way the /6 engine just fills the Frame, making it look very purposeful.

    So much nicer than the piles of Mono Bobshits one sees all over the place


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