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    #1

    bogging and backfiring

    Hi all, I am new to the forum and new to my GS450 bike. The previous owner abandoned the bike and has left it for me and my fraternity brothers to use. I have not spoken to him recently and thus do not know what year it is. I do know that it has CV type carbs. I have done a full cleaning on the carb. It has very good spark (new plugs too) and compression and always starts on the first try. Here are the problems: It backfires, mostly when letting off of the throttle, at all rpms. Also, it idles fine (except for the backfiring) and runs great at high rpms (cruising on the highway) but bogs alot between 1000 and 3000 rpms. To get around this I have to get it up to 3k rpms before taking off (if I let off the throttle and try to give it more gas again it bogs). Sometimes when I rev the engine it will "stick" at 3k rpms but will come back to idle if I rev it up to about 5k or 6k rpms (the throttle cable is not sticking, I quadruple checked it). I have checked the floats and the needles are not sticking, and the bowls are getting plenty of gas. Another thing to note is that I have drilled the (air screw?) plugs out, but have not yet tried adjusting them as I do not know if this is the problem. Everything on the motor is stock. I have spent 2 weeks trying to get her to run right but the low rpm range just plain sucks. Any help would be greatly appreciated as I am at a loss as to what is the next step in diagnosing these problems. Thanks in advance for any replys.

    Chris
    Tags: None
    #2
    Re: bogging and backfiring

    The symptoms you describe would be the result of an induction tube leak on the induction tubes between the carbs and the cylinder head.
    Doe your engine have "spigots" on the cylinder head and use round sections of "hose" to connect the head to the carbs, or does your engine use a flanged end induction tube? If a flanged tube, then there is a groove in the flange for an "O" ring seal and that sealing ring is probably dried out and cracked.

    Earl



    Originally posted by biznaller
    Hi all, I am new to the forum and new to my GS450 bike. The previous owner abandoned the bike and has left it for me and my fraternity brothers to use. I have not spoken to him recently and thus do not know what year it is. I do know that it has CV type carbs. I have done a full cleaning on the carb. It has very good spark (new plugs too) and compression and always starts on the first try. Here are the problems: It backfires, mostly when letting off of the throttle, at all rpms. Also, it idles fine (except for the backfiring) and runs great at high rpms (cruising on the highway) but bogs alot between 1000 and 3000 rpms. To get around this I have to get it up to 3k rpms before taking off (if I let off the throttle and try to give it more gas again it bogs). Sometimes when I rev the engine it will "stick" at 3k rpms but will come back to idle if I rev it up to about 5k or 6k rpms (the throttle cable is not sticking, I quadruple checked it). I have checked the floats and the needles are not sticking, and the bowls are getting plenty of gas. Another thing to note is that I have drilled the (air screw?) plugs out, but have not yet tried adjusting them as I do not know if this is the problem. Everything on the motor is stock. I have spent 2 weeks trying to get her to run right but the low rpm range just plain sucks. Any help would be greatly appreciated as I am at a loss as to what is the next step in diagnosing these problems. Thanks in advance for any replys.

    Chris
    All the robots copy robots.

    Komorebi-The light filtering through the trees.

    You are free to choose, but you are not free from the consequences of your choices.

    Comment

      #3
      bogging and backfiring

      I don't really understand how to tell what kind of induction tubes I have. There are 2 screws holding the tube to the jug and the tubes go out to the carbs, when I put the carbs in there is a groove on the carbs that the tubes snug into, there is a clamp on each carb side of the tubes. I synced the carbs today and got it to stop reving itself up and sticking at 3k rpms, but anything from idle to 2.5k is bogging. As a test i sprayed some starter fluid around where the induction tubes meet the jug and it didn't rev up. I was reading some other posts about similar problems and some have said airscrew adjustment but my plugs are a nice brown and others have said that some air pilot jet may need to be adjusted but my carbs have no such jet. Anyone have any ideas, I am baffled. I guess if its the only option I'll have to check out the seal from the tubes to the jug.

      Comment

        #4
        Biz,

        Earl is talking about this O-ring (red arrow)

        Frosty (falsely accused of "Thread-Hijacking"!)
        "Make it idiot proof and someone will make a better idiot."

        Owner of:
        1982 GS1100E
        1995 Triumph Daytona 1200

        Comment

          #5
          Thank you, thank you, thank you. :-) :-)

          Earl


          Originally posted by frosty5011
          Biz,

          Earl is talking about this O-ring (red arrow)

          All the robots copy robots.

          Komorebi-The light filtering through the trees.

          You are free to choose, but you are not free from the consequences of your choices.

          Comment

            #6
            Hey Earl,

            Sorry about that......but just had too darn many people always confused about what o-rings you meant

            As many times as it comes up, hell......it should be right under the "Carb Cleanup Series".
            Frosty (falsely accused of "Thread-Hijacking"!)
            "Make it idiot proof and someone will make a better idiot."

            Owner of:
            1982 GS1100E
            1995 Triumph Daytona 1200

            Comment

              #7
              Hey, I ws serious. You saved me many paragraphs of written explanation.
              I'll take all the help I can get. ehehe thanks again

              Earl


              Originally posted by frosty5011
              Hey Earl,

              Sorry about that......but just had too darn many people always confused about what o-rings you meant

              As many times as it comes up, hell......it should be right under the "Carb Cleanup Series".
              All the robots copy robots.

              Komorebi-The light filtering through the trees.

              You are free to choose, but you are not free from the consequences of your choices.

              Comment

                #8
                bogging and backfiring

                Thanks for the info, I had checked out from some other posts what those O rings were and how to check for a bad one (gap in the ring). Took the bike out today and rode her around for about an hour. I noticed a fuel smell, but no gas is leaking from the float overflow tubes and the plugs are not fouled. Am I supposed to be smelling a little gas, could it just be the exhaust?. Just thought I'd let you guys know cuz I never noticed it before. After my finals I'm gonna pull those flanges off and check those O rings. Another thing to note is that the clamps from the carb to induction tube seem like they bottom out before they really start squeezing the tube to the carb, how tight are these things supposed to be? Thanks guys

                Chris

                Comment

                  #9
                  I have a friend who's GS850 had a crack in one of the induction boots, and it would spray gas out of it, and onto his leg. I imagine a bad o-ring could do the same thing.

                  Comment

                    #10
                    Re: bogging and backfiring

                    Chris, considering the age of your bike and the probability those "O" rings have never been replaced, I think it would be a good idea to Bite The Bullet, and spend the big bucks for new ones. Two "O" rings should grand total out at about $2.50, and you will no longer have to wonder. :-) :-)

                    If youre smelling gas, there are only a couple possibilities. Leaking petcock, leaking or loose fuel line, leaking float valve seals. floats set to too high a level and the overflow tubes dripping. Bike stored in a hot place and fumes leaking from the gas tank vent.

                    Earl


                    Originally posted by biznaller
                    Thanks for the info, I had checked out from some other posts what those O rings were and how to check for a bad one (gap in the ring). Took the bike out today and rode her around for about an hour. I noticed a fuel smell, but no gas is leaking from the float overflow tubes and the plugs are not fouled. Am I supposed to be smelling a little gas, could it just be the exhaust?. Just thought I'd let you guys know cuz I never noticed it before. After my finals I'm gonna pull those flanges off and check those O rings. Another thing to note is that the clamps from the carb to induction tube seem like they bottom out before they really start squeezing the tube to the carb, how tight are these things supposed to be? Thanks guys

                    Chris
                    All the robots copy robots.

                    Komorebi-The light filtering through the trees.

                    You are free to choose, but you are not free from the consequences of your choices.

                    Comment

                      #11
                      bogging and backfiring

                      I found a site that has lots of parts for gs450's (including those orings at 5 bucks a set) but I have no idea what year or specific model it is. Does anyone know how to identify the bike? The only things I found were on a plate on the motor "GS450 113309". Thanks

                      Chris

                      Comment

                        #12
                        Chris / Biz,

                        You don't have any mfg date stamped up front on the frame anywhere? How about paperwork with the bike?
                        Frosty (falsely accused of "Thread-Hijacking"!)
                        "Make it idiot proof and someone will make a better idiot."

                        Owner of:
                        1982 GS1100E
                        1995 Triumph Daytona 1200

                        Comment

                          #13
                          bike identification

                          No paperwork as of yet (gotta wait till my bro mails it to me). Where abouts on the frame should I be looking, should I pull the gas tank off?

                          Chris

                          Comment

                            #14
                            Usually there's a plate riveted/attached up on the frame, in the front, by the steering stem.....with all the appropriate info on it (behind the headlight).
                            Frosty (falsely accused of "Thread-Hijacking"!)
                            "Make it idiot proof and someone will make a better idiot."

                            Owner of:
                            1982 GS1100E
                            1995 Triumph Daytona 1200

                            Comment

                              #15
                              identification

                              Thanks for the tip, found out she's an '80.

                              Chris

                              Comment

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