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  4. CB750 scrambler project

CB750 scrambler project

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  • Louis-DT-WRL Offline
    Louis-DT-WRL Offline
    Louis-DT-WR
    wrote on last edited by
    #76
    This post is deleted!
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    • Louis-DT-WRL Offline
      Louis-DT-WRL Offline
      Louis-DT-WR
      wrote on last edited by
      #77

      Its a wasted spark system btw

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      • CalumC Calum

        Depends where you are measuring from. The coils job is to take the 12V DC and step it up to 20KV. So you measuring at 12V is outside the scopes range.

        12V isn't enough to jump the spark plug gap.

        Measuring Coils is usually done through impedance test on the primary to secondary, secondary to spark plug cap. Should fall within the tolerances outlined by the manufacturer.

        Louis-DT-WRL Offline
        Louis-DT-WRL Offline
        Louis-DT-WR
        wrote on last edited by
        #78

        @Calum thanks, I'm pretty sure both coils are bad. No resistance at all between power/trigger and the caps.

        They were second hand, came with the loom.

        12.8 volts on the looks power connectors.

        New coils, leads and caps on order 🤞

        I

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        • S Offline
          S Offline
          SpookDog
          wrote on last edited by
          #79

          Wasted spark is when they both spark at top dead centre?
          Have you not gotten any old coil off of another bike? Even a single one that you can get to spark? It would at least prove the rest of the circuit was on par...

          Louis-DT-WRL 1 Reply Last reply
          1
          • S SpookDog

            Wasted spark is when they both spark at top dead centre?
            Have you not gotten any old coil off of another bike? Even a single one that you can get to spark? It would at least prove the rest of the circuit was on par...

            Louis-DT-WRL Offline
            Louis-DT-WRL Offline
            Louis-DT-WR
            wrote on last edited by
            #80

            @SpookDog yes wasted spark system is that.

            I've ordered new coils as the primary has 3 ohms which is fine but secondary resistance has no resistance at all. On both. This is 1 fault. I'll have to see if there is others.
            They are very old and probably corroded inside

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            • Louis-DT-WRL Offline
              Louis-DT-WRL Offline
              Louis-DT-WR
              wrote on last edited by
              #81

              This is the confusion I have , electrics are not my strongest point.

              The manual says the yellow/blue wire goes at the top connector on both coils...

              alt text
              alt text

              The coils are not handed so the green terminal is at the top on one side and black at the bottom when installed.

              alt text

              alt text

              That's a what's confusing me 🤔
              I'm still waiting for the new plug caps to try.

              I'm also not sure if I need to loop the sidestand indicator light as I removed it... I'm pretty sure it just piggybacks

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              • S Offline
                S Offline
                SpookDog
                wrote on last edited by
                #82

                If it’s connected to the ignition it could be the cause of your problem, specially if you’re neutral lights not working...

                Louis-DT-WRL 1 Reply Last reply
                1
                • S SpookDog

                  If it’s connected to the ignition it could be the cause of your problem, specially if you’re neutral lights not working...

                  Louis-DT-WRL Offline
                  Louis-DT-WRL Offline
                  Louis-DT-WR
                  wrote on last edited by
                  #83

                  @SpookDog alt text

                  Do you think that's the problem looking at this?

                  To me it looks like if the neutral light is on (which it is) it should start.

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                  • CalumC Offline
                    CalumC Offline
                    Calum
                    wrote on last edited by
                    #84

                    So it looks like according to the diagram that the G/W wire needs to be tied to Earth if you want to bypass the side stand switch. The Y/Bl wire can just be taped up. I.E. don't complete the circuit for that.

                    Always Originate, Never Pirate!

                    Louis-DT-WRL 1 Reply Last reply
                    0
                    • CalumC Calum

                      So it looks like according to the diagram that the G/W wire needs to be tied to Earth if you want to bypass the side stand switch. The Y/Bl wire can just be taped up. I.E. don't complete the circuit for that.

                      Louis-DT-WRL Offline
                      Louis-DT-WRL Offline
                      Louis-DT-WR
                      wrote on last edited by
                      #85

                      @Calum I have the sidestand switch, all plugged in. Only the indicator light isn't connected. Does that affect it? Cheers.

                      Also still confused on the wires to the green or black connectors on the coils.

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                      • CalumC Offline
                        CalumC Offline
                        Calum
                        wrote on last edited by
                        #86

                        The light only needs to be there if the side stand is down by the looks of it.

                        Always Originate, Never Pirate!

                        Louis-DT-WRL 1 Reply Last reply
                        0
                        • CalumC Calum

                          The light only needs to be there if the side stand is down by the looks of it.

                          Louis-DT-WRL Offline
                          Louis-DT-WRL Offline
                          Louis-DT-WR
                          wrote on last edited by
                          #87

                          @Calum that's what I'm thinking but if in neutral then it shouldn't Matter ,?

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                          • S Offline
                            S Offline
                            SpookDog
                            wrote on last edited by
                            #88

                            I can’t get my head round the diagram at the mo. There are a lot of differences from what I know. What about the diode (number 7) condition?
                            I know that the live wires on the coils will only affect spark timing if wrong, they should still spark. So I’m guessing that the problem is with the side stand, neutral, cutout circuit somewhere, if there’s no spark still...
                            Sorry I can’t be more help at the mo’. Too many brewskies!🤪

                            Louis-DT-WRL 2 Replies Last reply
                            0
                            • S SpookDog

                              I can’t get my head round the diagram at the mo. There are a lot of differences from what I know. What about the diode (number 7) condition?
                              I know that the live wires on the coils will only affect spark timing if wrong, they should still spark. So I’m guessing that the problem is with the side stand, neutral, cutout circuit somewhere, if there’s no spark still...
                              Sorry I can’t be more help at the mo’. Too many brewskies!🤪

                              Louis-DT-WRL Offline
                              Louis-DT-WRL Offline
                              Louis-DT-WR
                              wrote on last edited by
                              #89

                              @SpookDog yes it's a crappy diagram, I assume the second bulb is the neutral one.

                              I've never had a diode go wrong on anything but might test it.
                              I think it's the side stand ... I'll do more tests when the plug caps come.

                              Thanks

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                              • S SpookDog

                                I can’t get my head round the diagram at the mo. There are a lot of differences from what I know. What about the diode (number 7) condition?
                                I know that the live wires on the coils will only affect spark timing if wrong, they should still spark. So I’m guessing that the problem is with the side stand, neutral, cutout circuit somewhere, if there’s no spark still...
                                Sorry I can’t be more help at the mo’. Too many brewskies!🤪

                                Louis-DT-WRL Offline
                                Louis-DT-WRL Offline
                                Louis-DT-WR
                                wrote on last edited by
                                #90

                                @SpookDog I think if I try to crank the engine over (on the starter motor) in gear but with the clutch switch pulled in... That would also prove if the silicon diode is faulty 🤔

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                                • S Offline
                                  S Offline
                                  SpookDog
                                  wrote on last edited by
                                  #91

                                  A diode only lets electric pass one way I think. I’d try a continuity/bulb test

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                                  • S Offline
                                    S Offline
                                    SpookDog
                                    wrote on last edited by
                                    #92

                                    Yeah, it should only show continuity one way. Do a quick google for diode testing...

                                    Louis-DT-WRL 1 Reply Last reply
                                    0
                                    • S SpookDog

                                      Yeah, it should only show continuity one way. Do a quick google for diode testing...

                                      Louis-DT-WRL Offline
                                      Louis-DT-WRL Offline
                                      Louis-DT-WR
                                      wrote on last edited by
                                      #93

                                      @SpookDog thanks.. I tested the resistance and compared it to my spare one, seemed fine. I'm pretty sure it's the sidestand circuit....

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                                      • S Offline
                                        S Offline
                                        SpookDog
                                        wrote on last edited by
                                        #94

                                        I recon it is as well. I’d connect the side stand and clutch switch stuff all up, put it in neutral and try it with the clutch pulled in.
                                        With the coil connectors, I’d try one ‘one way’ and the other the ‘other way’ if that makes sense? One of them should spark. Once they are sparking it’s easy to figure out which is the outer banks and which is inner...
                                        Good luck my amigo!

                                        Louis-DT-WRL 1 Reply Last reply
                                        0
                                        • S Offline
                                          S Offline
                                          SpookDog
                                          wrote on last edited by
                                          #95

                                          a Diode is like a one way valve for electric. The live wire on the anode and earth on the cathode should have continuity (power flowing through). Reverse the wires and there should be none.

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