Coil BBQ

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  • hazydaze
    Member
    • Jan 2016
    • 35

    Coil BBQ

    Okay, so let me start by giving some info on my set up: it is a 76 sporty ive built from scratch. The wiring was finished yesterday (or so I thought) but just now I smell some smoke and go check... the coil has melted all over my primary and is HOT to touch. this is after i watched it spark and i watched the points spark as well. now, the key was off and all wires were fine and cool to touch. I have done some reading and what ive found is that it is possible that if the points were touching then the coil is receiving current through the neg terminal thus potentially causing a problem, which may be a plausible explanation since i have not yet timed my points its just been stuck in there... aaannndd also now my points seem to be fried since they no longer spark. Second thing is that I did not know a coil needs some sort of resistor( and i am still not sure) ; i popped some random harley coil on there and stuck a couple homemade spark plug wires on it and forgot about it but now I just saw some video of a guy explaining the point of a resistor in the spark plug boot which made me recognize my mistake... my boots do not have resistors simply a wire clamped in and shoved on to the coil. so i am thinking that with no resistors, and the points making contact to the neg terminal for about an hour potentially fried my coil. also, i just assumed that the negative terminal on the coil was whichever is hooked up to the points so i never tested it! that's probably a cause too! dang always somethin huh

    I'll describe my wiring: i am running everything to a 3 pos key switch. I have ign/batt/reg on the 1st position, and the lights on the second position. there is a small fuse between the batt and the key switch. my idea was that i could run the bike w no lights if needed and click the key one more time to turn them on. no elect. starter

    So that is my newest problem, maybe anyone with more knowledge than i have about this will be kind enough to drop a little on me
  • tzienlee
    • Mar 2024

    #2
    the resistor in the plug cap is only there to stop radio & TV interference so don't worry about not having them,... if anything they weaken the spark, on magnetos it is advised you do not use resistor plugs or plug caps.
    now I don't know how you have wired it, but in very basic terms, I run a wire from the switch + feed to the coil and from the - on the coil to the points, that way it only gets power when ignition is on,
    if you have power going to the coil all the time and just rely on the points being open to be the isolator switch there lies your problems
    either that or you left the ignition switch on and cooked the coil that way...…………..
    Attached Files
    Last edited by Guest; 09-12-2018, 2:33 AM.

    Comment

    • rockman96
      Senior Member
      • May 2018
      • 893

      #3
      As stated above, you want power to be going thru the ignition switch... not on all the time.

      Just so you know how the points work... a coil is basically two separate windings of wire around an iron core. A step-up transformer. When there is power to the coil you have created a magnetic field from the primary side. For the instant that the points open, you have caused the field to collapse (this is fast and violent) which induces a stepped up voltage on the secondary... this is your spark.

      I know you did not ask how it works, but when you can visualize something it can help with your troubleshooting. The points are closed most of the time, and only open for a brief duration of the engine revolution.

      Comment

      • hazydaze
        Member
        • Jan 2016
        • 35

        #4
        Thanks, this is how I've got it nowClick image for larger version

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        Comment

        • TriNortchopz
          Senior Member
          • Dec 2017
          • 3246

          #5
          What about a fuse (or circuit breaker), or a couple even,,,
          If buildin' old school choppers was easy, anyone could do it... ain't nobody said it's gonna be easy...

          Comment

          • Tattooo
            Senior Member
            • Sep 2012
            • 12407

            #6
            It's hard to tell where the wires are on the switch but are your lights on when you cut the switch on? I know there not on all the time and you turn them off with that light switch...

            Comment

            • TriNortchopz
              Senior Member
              • Dec 2017
              • 3246

              #7
              And remember when runnin' points, your coil should be 5 ohm primary resistance.
              If buildin' old school choppers was easy, anyone could do it... ain't nobody said it's gonna be easy...

              Comment

              • hazydaze
                Member
                • Jan 2016
                • 35

                #8
                I have since installed a little circuit breaker that will shut the bike off if anything starts to burn up. I do not think it was a 5ohm coil. the light switch is just hi/lo beam, but the wiring on the key switch is this: switch has 3 prongs labelled G, Batt, St. Everything works w/o hooking up the G terminal on the switch so I have the regulator, the battery hot, and the coil hot going to the first click Batt and then the lights are on the second click St. my original diagram which i posted is the template i used to hook up all the components but i decided to run the lights on their own terminal and the ignition/batt/ charging system on the other so that I could theoretically run the bike w/o lights and simply turn one click on the key to have lights. I pulled that diagram off XL forum or something and thought I would change the set up to suit my needs but now I am going to rewire my key switch to what is shown in the diagram since this is my first time wiring a bike from scratch it might be better to just do it the way it worked for someone else. I also got some new points since mine were burned up, and I ordered a Dynatek S dual fire kit #DSK6-1 to try out just for comparabilities sake so when i run in to more problems and figure out my solutions I'll try to remember to take some pics and post how i figured it out for anyone else who might be interested

                Comment

                • TriNortchopz
                  Senior Member
                  • Dec 2017
                  • 3246

                  #9
                  This series of threads may be of interest:

                  Wiring your chopper...


                  which includes this thread:

                  Basic Wiring diagramme...

                  "This thead has been set up in response to requests for chopper wiring information.

                  What follows is an attempt to make wiring your chopper understandable, and I'll say from the outset that I am not a motorcycle electrician... and you don't need to be either... just wire up your bike and ask questions as you need to"...


                  If buildin' old school choppers was easy, anyone could do it... ain't nobody said it's gonna be easy...

                  Comment

                  • hazydaze
                    Member
                    • Jan 2016
                    • 35

                    #10
                    thanks, I'll check out those threads

                    and as I said before I was getting that dyna s ignition to "replace" my points. it arrived the other day, I installed it and could feel a noticeable difference in the bite of the spark from the points to the electric unit, and I also managed to sort out my wiring in the rest of the bike. next I'll refurbish the advance weights, time it, valves...then I'll kick away until it starts. I'll find the thread to post the running bike when that happens, and thanks for the advice everyone

                    hd

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