2-3 coil keeps burning up

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  • gs850cafe
    • Jan 2026

    #1

    2-3 coil keeps burning up

    what the hell is causing this? i had some spare coils...they would last about 1000 or so miles an quit..always number 2-3

    bike is a 81 850..

    has new caps an everything as well
  • tom203
    Forum Guru
    Past Site Supporter
    • Aug 2010
    • 8925
    • Norway,Maine

    #2
    "some spare coils" ? suzuki ones- about 4 ohm primary? Is your ignitor surviving this coil torture with no ill effects?
    1981 gs650L

    "We are all born ignorant, but you have to work hard to stay stupid" Ben Franklin

    Comment

    • gs850cafe

      #3
      Originally posted by tom203
      "some spare coils" ? suzuki ones- about 4 ohm primary? Is your ignitor surviving this coil torture with no ill effects?
      yes suzuki coils off another gs850...igniter seems to be fine...i put a spare coil on an off i go with no issues...

      Comment

      • tom203
        Forum Guru
        Past Site Supporter
        • Aug 2010
        • 8925
        • Norway,Maine

        #4
        Wow, this is strange-all the ignitor does is ground out coil- it should have no way to boost extra current thru it . Do you still have a 10 amp ignition fuse?
        1981 gs650L

        "We are all born ignorant, but you have to work hard to stay stupid" Ben Franklin

        Comment

        • BassCliff

          #5
          Hi,

          I would start by taking off the tank and seat to perform a close visual inspection. Check for worn or melted insulation. Make sure there are no components touching metal. Go over the wiring harness with a fine-toothed comb. Check the resistance on the plug caps.

          This has been my "profound glimpse into the obvious" for today.


          Thank you for your indulgence,

          BassCliff

          Comment

          • gs850cafe

            #6
            Originally posted by tom203
            Wow, this is strange-all the ignitor does is ground out coil- it should have no way to boost extra current thru it . Do you still have a 10 amp ignition fuse?
            ahh that im not sure of..ive just taken them out to clean them..

            also clif ive pretty well done what u said..plus the relay mod..

            i was so ****ed this mornin i forgot to mention that..

            but im glad its no my igniter doing it then

            Comment

            • SqDancerLynn1

              #7
              Have you done the voltage regulator circuit !!!

              Comment

              • gs850cafe

                #8
                ok so apparently my ignition fuse had a 20 amp in it...replaced it with a 10...ill post results if it changes

                also its the 3rd or 4th fuse from the top right?(81 850)

                Comment

                • posplayr
                  Forum LongTimer
                  GSResource Superstar
                  Past Site Supporter
                  • Dec 2007
                  • 23673
                  • Tucson Az

                  #9
                  the only things that might cause a coil to burn would be either
                  • you leave the key on so long that the coil over heats and the insulation breaks down causing a short.
                  • Or vibration induced failure of the coil insulation

                  The fuse should not change anything unless it blows then you know there is a potential short in the coil. You could measure the resistance 3-4 ohms .
                  Also confim the current through a coil is approx:
                  12V/3ohms=4 amps
                  or
                  12V/4ohms=3 amps

                  Do you smell smoke or burnt material?

                  Comment

                  • gs850cafe

                    #10
                    Originally posted by posplayr
                    the only things that might cause a coil to burn would be either
                    • you leave the key on so long that the coil over heats and the insulation breaks down causing a short.
                    • Or vibration induced failure of the coil insulation

                    The fuse should not change anything unless it blows then you know there is a potential short in the coil. You could measure the resistance 3-4 ohms .
                    Also confim the current through a coil is approx:
                    12V/3ohms=4 amps
                    or
                    12V/4ohms=3 amps

                    Do you smell smoke or burnt material?
                    nope no coils smell burnt..i tested my spares, they were all in check when put on, then when they test out of spec

                    Comment

                    • posplayr
                      Forum LongTimer
                      GSResource Superstar
                      Past Site Supporter
                      • Dec 2007
                      • 23673
                      • Tucson Az

                      #11
                      Originally posted by gs850cafe
                      nope no coils smell burnt..i tested my spares, they were all in check when put on, then when they test out of spec
                      what spec? what measurements?

                      Comment

                      • gs850cafe

                        #12
                        Originally posted by posplayr
                        what spec? what measurements?
                        iu dont rmeber off hand.. i think on being 6-7 ohm and 11-12k on wire side

                        Comment

                        • duaneage
                          Forum Guru
                          GSResource Superstar
                          • Apr 2004
                          • 6149
                          • Wilmington Delaware

                          #13
                          Maybe the terminology is a problem. When you say "burning up" do you mean the coil is melting and leaking wax or that the coil develops an open connection on either the primary or secondary side?
                          1981 GS650G , all the bike you need
                          1980 GS1000G Power corrupts, and absolute power corrupts absolutely

                          Comment

                          • gs850cafe

                            #14
                            no the coil looks fine..

                            but today i was out of town an it acted up when i hit a bump...im like omg already...so i yanked off my tank on the side of the road to find a bad connector...so off it came an i taped it up an rode it all day with no issues...

                            can a loose/poor connection ruin a coil?

                            Comment

                            • duaneage
                              Forum Guru
                              GSResource Superstar
                              • Apr 2004
                              • 6149
                              • Wilmington Delaware

                              #15
                              A bad connection is not likely to ruin a coil, but it might convince you the coil is bad. They are just spools of wire sealed in a case, and pretty robust at that. Better coils exist but the GS coils get the job done.
                              1981 GS650G , all the bike you need
                              1980 GS1000G Power corrupts, and absolute power corrupts absolutely

                              Comment

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