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Question: Firing order on GS 750?

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    Question: Firing order on GS 750?

    Hello, I will introduce myself a little later, but right now I need to get down to business. I bought a complete, but complete basketcase, GS750. Gave the carbs to a friend to rebuild. While waiting for the carbs, I am turning my attention to everything else it needs.

    I installed a new set of points, and was about to install ignition wires and plugs when I noticed some interesting hand-etched markings on the coils. The coil on the right side of the bike is marked "2" and "3," and its two spark wires run to the right two cylinders, which I assume are cylinder numbers 3 and 4. The coil on the left side is marked "1" and "4," and its two wires run to what I assume are cylinders 1 and 2 (the left two cylinders.) The markings I refer to are etched by hand into the coils, very likely not factory markings.

    Somebody please help me decipher these markings and tell me the firing order and how Suzuki numbered the cylinders in the first place.

    As for the markings, the only thing I can figure is that maybe somebody once marked the coils by their position in the firing order. The wires are currently installed 4-1-2-3 (assuming the left cylinder is number one) according to the markings on the coils.

    This does appear to be a waste fire arrangement, which would go with how the coils are marked, because the 1-4 pair and the 2-3 pair would fire at the same time if the crankshaft is the normal I4 type with 1 and 4 being 180 crank degrees out from 2 and 3. That said, the way the wires are installed, I can't see how the bike would run.

    Am I making sense? Does anybody understand what I am dealing with? Can somebody cut through all of this and tell me where to put which wire? I wouldn't mind playing musical wires, but I got a build-it-yourself wire kit, so I want to make the wires fit nice and tidy.

    And yes, I will be buying a service manual. I just need information now. Thanks.

    #2
    Coils are marked incorrectly by a previous owner ! left coil as you are sat on the bike should be for cylinders 1&4 right coil for 2&3

    Comment


      #3
      First of all,


      Now, the cylinders are numbered from left to right, as you sit on the bike. #1 is under your clutch hand, #4 is under your throttle hand.

      The coils do fire in a wasted spark setup as you suspect. As currently wired, the bike will not run. The markings on the coils are OK, but the wire routing is not. As mentioned by tone, #1 and #4 should be fired by the left coil and #2 and #3 should be fired by the right coil.

      The firing order is 1 - 2 - 4 - 3.

      BassCliff will be along shortly with his little welcome thing, but if you go to his website and bookmark it, you will find copies of service manuals that you can download. It's always nice to have more than one version, though. I have found differences between the factory manual, Clymer and Haynes that make it worth having all three.

      .
      sigpic
      mine: 2000 Honda GoldWing GL1500SE and 1980 GS850G'K' "Junior"
      hers: 1982 GS850GL - "Angel" and 1969 Suzuki T250 Scrambler
      #1 son: 1986 Yamaha Venture Royale 1300 and 1982 GS650GL "Rat Bagger"
      #2 son: 1980 GS1000G
      Family Portrait
      Siblings and Spouses
      Mom's first ride
      Want a copy of my valve adjust spreadsheet for your 2-valve per cylinder engine? Send me an e-mail request (not a PM)
      (Click on my username in the upper-left corner for e-mail info.)

      Comment


        #4
        Originally posted by tone View Post
        Coils are marked incorrectly by a previous owner ! left coil as you are sat on the bike should be for cylinders 1&4 right coil for 2&3
        OK. That gets me half way there. Is this a waste fire arrangement? If so, as long as one wire goes to 1 and one to 4 (2 and 3 on the other side,) then it doesn't matter. If it is not waste fire, then I need to know which one goes to one and which one to four, etc. But it must be waste fire, right?

        Also, all four of the small wires (secured with a stud and nut) are loose on the coils. From left to right, the colors are orange/white, black, white, orange/white. These wires are loose, but are they in the correct order?

        Comment


          #5
          OK, then that answers everything except the new question I just asked about the exciter wires. Answers on that?

          Comment


            #6
            Yes, it is a wasted spark arrangement, it does not matter if the plug wires go on #1 or #4, the length of the wire should give you a hint.

            Not sure about your left-to-right arrangement for exciter wires, but both coils should have an orange/white wire connected.
            The left coil (1&4) should have the white wire connected.
            The right coil (2&3) should have the black wire.
            Look carefully at the 'black' wire. Any chance it's actually black and yellow?
            That's what the wiring diagrams show.

            .
            sigpic
            mine: 2000 Honda GoldWing GL1500SE and 1980 GS850G'K' "Junior"
            hers: 1982 GS850GL - "Angel" and 1969 Suzuki T250 Scrambler
            #1 son: 1986 Yamaha Venture Royale 1300 and 1982 GS650GL "Rat Bagger"
            #2 son: 1980 GS1000G
            Family Portrait
            Siblings and Spouses
            Mom's first ride
            Want a copy of my valve adjust spreadsheet for your 2-valve per cylinder engine? Send me an e-mail request (not a PM)
            (Click on my username in the upper-left corner for e-mail info.)

            Comment


              #7
              Greetings and Salutations!!

              Hi Mr. Longitudinal,

              You'll find lots of GS lovin' on my website. Please help yourself. Now let me say "HOooooowwDY!"

              Here is your very own magical, mystical, mythical, mind-expanding "mega-welcome". Please take notice of the "Top 10 Common Issues", the Carb Rebuild Series, and the Stator Papers. Now let me roll out the welcome mat for you...

              Please click here for your mega-welcome, chock full of tips, suggestions, links to vendors, and other information. Then feel free to visit my little BikeCliff website where I've been collecting the wisdom of this generous community. Don't forget, we like pictures! Not you, your bike!

              Thanks for joining us. Keep us informed.

              Thank you for your indulgence,

              BassCliff

              Comment


                #8
                I am well on my way to getting this GS750 together, thanks to this community. Thank you all for the welcomes. I just looked up my battery specs on BassCliff's site and got that. It is filled and charging right now.

                I am ready to reinstall the fuel tank as well. Before I do this, should I automatically perform the coil relay trick? The scientist in me wants to change as few things as possible until I hear the bike run. The mechanic in me (also the lazy part) wants to do the mod now while the tank is off. Should I make sure I have a running bike first? The coil relay mod seems a sure thing, but modifying a vehicle that hasn't run in who-knows-how-long before it runs doesn't seem smart either.

                Also, I understand that each coil gets an o/w wire. To which terminals do they go, and to which to the black (right coil) and white (left coil) wires go? I have looked at the two 750 wiring diagrams on BikeCliff's site, but both depict the wires in question coming out opposite ends of each coil, whereas all four of mine (two on each coil) come out the same end (the fronts) of the coils.
                Last edited by Guest; 09-21-2009, 05:41 PM. Reason: Add information

                Comment


                  #9
                  We're up to the emergency level regarding the coil wires. I need to have this bike running today. Anybody care to help me regarding the black/yellow, orange/white and white wires and their locations on the coils?

                  I'll have to start guessing pretty soon.

                  TIA,
                  Jonathan
                  Last edited by Guest; 09-22-2009, 12:33 PM. Reason: correction

                  Comment


                    #10
                    O/W goes to the + terminal on both coils.
                    The other two go to the - terminal, one to each coil.


                    Life is too short to ride an L.

                    Comment

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