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    Sparking ignition points

    Hey guys. For a while now I've been reading and researching, trying to track down the cause of a misfire on my '79 GS750.

    The misfire only starts once the engine gets good and hot. I've read on the forums here about a few guys that had similar issue and it seems the most common suggestion was to replace the condensers. So i went online and ordered a tune up kit (points and condensers: www.ebay.co.uk/itm/392850752997 ).

    This evening installed everything from the kit and started the bike up with the cover still off. The bike runs, but I was surprised to see a lot of sparking on both points. I haven't taken it for a test ride yet with the new parts on it because I'm assuming that all those sparks means something isn't right.

    Could it be that the new condensers are somehow not grounded? Or maybe the parts i ordered are low quality? Could bad coils or wires be causing sparks at the points?? The points/condensers are the first things I've looked at, so maybe i should move up and check the coils and wires.

    Any and all suggestions or recommendations are greatly appreciated! Electronics are not my strong suit, but I'm doing my best to learn how these old bikes work so hopefullyI can get my old girl running a bit better.
    My bike: 1979 GS750E

    #2
    Add the bike to your signature please so in the future we dont have to repeatedly ask...thanks. MAYBE theres a service manual here. If not in main menu then click on CLICK HERE FOR MORE MANUALS.

    MY BIKES..1977 GS 750 B, 1978 GS 1000 C (X2)
    1978 GS 1000 E, 1979 GS 1000 S, 1973 Yamaha TX 750, 1977 Kawasaki KZ 650B1, 1975 Honda GL1000 Goldwing, 1983 CB 650SC Nighthawk, 1972 Honda CB 350K4, 74 Honda CB550

    NEVER SNEAK UP ON A SLEEPING DOG..NOT EVEN YOUR OWN.


    I would rather trust my bike to a "QUACK" that KNOWS how to fix it rather than a book worm that THINKS HE KNOWS how to fix it.

    Comment


      #3
      Originally posted by chuck hahn View Post
      Add the bike to your signature please so in the future we dont have to repeatedly ask...thanks.
      Done! I had said what model and year bike I had in the OP but now I’ve also added it to my signature
      My bike: 1979 GS750E

      Comment


        #4
        sorry....didnt catch it
        MY BIKES..1977 GS 750 B, 1978 GS 1000 C (X2)
        1978 GS 1000 E, 1979 GS 1000 S, 1973 Yamaha TX 750, 1977 Kawasaki KZ 650B1, 1975 Honda GL1000 Goldwing, 1983 CB 650SC Nighthawk, 1972 Honda CB 350K4, 74 Honda CB550

        NEVER SNEAK UP ON A SLEEPING DOG..NOT EVEN YOUR OWN.


        I would rather trust my bike to a "QUACK" that KNOWS how to fix it rather than a book worm that THINKS HE KNOWS how to fix it.

        Comment


          #5
          so choose the EARLY 8 VALVE service manual for the 750.
          MY BIKES..1977 GS 750 B, 1978 GS 1000 C (X2)
          1978 GS 1000 E, 1979 GS 1000 S, 1973 Yamaha TX 750, 1977 Kawasaki KZ 650B1, 1975 Honda GL1000 Goldwing, 1983 CB 650SC Nighthawk, 1972 Honda CB 350K4, 74 Honda CB550

          NEVER SNEAK UP ON A SLEEPING DOG..NOT EVEN YOUR OWN.


          I would rather trust my bike to a "QUACK" that KNOWS how to fix it rather than a book worm that THINKS HE KNOWS how to fix it.

          Comment


            #6
            If there's more than the tiniest spark appearing across the points when they open, the condensers are shot or not connected right.
            ---- Dave
            79 GS850N - Might be a trike soon.
            80 GS850T Single HIF38 S.U. SH775, Tow bar, Pantera II. Gnarly workhorse & daily driver.
            79 XS650SE - Pragmatic Ratter - goes better than a manky old twin should.
            92 XJ900F - Fairly Stock, for now.

            Only a dog knows why a motorcyclist sticks his head out of a car window

            Comment


              #7
              But that’s what I’m not understanding; the condensers are brand new. What are the odds they are both defective out of the box? And I’ve checked and double checked that everything is hooked up correctly - and as far as I can tell it is.

              what else could cause sparks jumping across the points??
              My bike: 1979 GS750E

              Comment


                #8
                Could you have inadvertantly put a fibre or insulating washer between the condenser lead and the points post?
                97 R1100R
                Previous
                80 GS850G, 79 Z400B, 85 R100RT, 80 Z650D, 76 CB200

                Comment


                  #9
                  Originally posted by Brendan W View Post
                  Could you have inadvertantly put a fibre or insulating washer between the condenser lead and the points post?
                  the condensers should be connected to the moving point, same as the wire from the coil - have I got that right?

                  ive got a photo of how I’ve wired it up, but I can’t figure out how to post it.
                  My bike: 1979 GS750E

                  Comment


                    #10
                    yes, sparks at the points doo scream "Condensor".....test for a good ground of the condensor's mount? There should be perfect continuity from it to the frame and the battery "-" post...so you can test that and be sure.

                    I looked at the ebay listing...I'm grasping at straws -you likely noticed it too, but
                    "
                    (((Nippondenso ignition, please check that you have Nippondenso ignition and not the Kokusan, this kit will not replace the Kokusan ignition))).
                    "
                    Last edited by Gorminrider; 09-29-2020, 11:45 AM.

                    Comment


                      #11
                      It's running, and the condensers are doing something, 'cos a knacked condenser causes endless misfires and you have two to do mischief on you.
                      So, if it's not actually misfiring the condensers are working, but probably not really as well as they should be - aftermarket ignition bits are notoriously unreliable or under-specced, condensers especially.
                      However, having said that, I distinctly recall many Japanese points-equipped bikes sparking a bit between the points, a lot more than I felt was right, but the engines were running fine. I suspect it's just down to the limitation of size imposed on the design because of where they have to fit, leading to a smaller capacitance than a normal car condenser would be in the same circumstance.
                      From memory, car condensers range from 1 to 5uF-ish. I don't recall what the Zuk ones are.
                      ---- Dave
                      79 GS850N - Might be a trike soon.
                      80 GS850T Single HIF38 S.U. SH775, Tow bar, Pantera II. Gnarly workhorse & daily driver.
                      79 XS650SE - Pragmatic Ratter - goes better than a manky old twin should.
                      92 XJ900F - Fairly Stock, for now.

                      Only a dog knows why a motorcyclist sticks his head out of a car window

                      Comment


                        #12
                        Originally posted by Gorminrider View Post

                        I looked at the ebay listing...I'm grasping at straws -you likely noticed it too, but
                        ""[/FONT]
                        i definitely ordered the correct Nippon ones for my bike. Pretty sure the others wouldn’t fit anyways.
                        My bike: 1979 GS750E

                        Comment


                          #13
                          Originally posted by Grimly View Post
                          So, if it's not actually misfiring the condensers are working, but probably not really as well as they should be - aftermarket ignition bits are notoriously unreliable or under-specced, condensers especially.
                          However, having said that, I distinctly recall many Japanese points-equipped bikes sparking a bit between the points, a lot more than I felt was right, but the engines were running fine.
                          I guess i'll button it all up and take her for a ride. The whole reason i started into the ignitions bits was cause of a misfire when the engine is hot, so I'd better get the engine good and warm and see if the misfire is still there. If it is, maybe it's time to pull the trigger on one of them fancy Dynatek electronic ignitions.

                          By the way, here's the photo of how i've got the points and condensers wired. I realize it's hard to see anything, but maybe one of you wise people can spot something i've missed??
                          Attached Files
                          My bike: 1979 GS750E

                          Comment


                            #14
                            That'd be a shame if you don't know what is wrong with the OEM. If you give up and gofor the $$$ solution, you'd want to get ALL new....new coils with new plug-leads+ new plugs as well to be sure you'll have a totally fresh playing field....so, I'd check all these before I gave up and parted with the money. Not because I'm skint but because even more things might be involved. A key switch, or a loose battery connection or perhaps a leaky stator wire? (I've never seen this but it came up in a very similar thread...https://www.thegsresources.com/_foru...id-range-issue) you will be really unhappy if the new stuff doesn't cure it.

                            It'd really help to identify if ALL cylinders are misfiring or just 1 or 2. These "only when hot" problems can be hard to find but can you warm the bike up in the shop or driveway and look for it then?
                            Last edited by Gorminrider; 10-01-2020, 11:46 AM.

                            Comment


                              #15
                              Just a quick update. Despite some arcing at the new points, I closed everything up and took the bike for a test ride. The result; the misfire appears to be gone! It seems likely that the old condensers were the main cause of the misfire that I was getting when the engine got hot.

                              Strange about the arcing but I guess as one of you said, maybe it’s just normal for these bikes?

                              Thanks for all the help and suggestions gentlemen!
                              My bike: 1979 GS750E

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