750B cafe project.pops and bogs down.

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  • solarplex
    #1

    750B cafe project.pops and bogs down.

    Hello everyone,
    1977 GS750B. I have cleaned the carbs thoroughly and replaced the O-rings. Replaced the air-box with pod filters. Cleaned all grounded wires and replaced battery. Checked the plugs and wired(new plugs,wire insulators are good).
    The bike starts very easy. Second kick or quick crank with the electric starter.
    Problems are as follows:will idle but pops and snaps intermittantly,shoots flame out left bank pipe(OEM type 2 to 1)but not right side. Slow to respond and occationally wants to choke(bog down) when i twist quickly from idle. Seems to smoothe out and snaps quickly to higher RPM once the engine (catches-up) but if held to 3,4,5,6,7 ect. RPM, it still pops and snaps. It doesnt seem like a (MISS) but maybe like it is getting too much fuel to air.
    Any reccomendations as to how many turns out(to start with) on the (air screws) and the other screws under the carbs. next to the bowl drain.?
    This bike ran like this even before i replaced the air-box with the pods and it doesnt seem any worse,if anything, it seems to run better.
    Any expert,professional or experienced response is very appreciated.
    Tags: carbs, gs750, popping
    • TheCafeKid
      #2
      Airscrews arent going to help you here. If youve replaced the airbox with pods, and havent re-jetted the carbs, currently you are damaging your motor by running it at all. Removing the airbox in place of pod filters makes your system extremely lean. Lean will burn valves, piston rings, and cylinder walls. This could quickly spell death for your motor..Are you running a 4into1 pipe? If so, you are even leaner still. You cannot even get it close without changing the main jet, and moving the needle in each carb. Your stock pilot jets should be just fine. Let me know what set up for exhaust and what type of pods you are running, and I can be of more help. I have the same bike, and its also my cafe project, with a VH 4into1 and pods, so i can give you a good base of where to start with your jetting. Unfortunately, there is no Dynojet kit for our 750s so it has to be done by hand. Not tough tho..

        Comment

        • solarplex
          #3
          CafeKid,
          Thanks for such a fast response. I have not run this bike much,..just enough to get it to temp. once.
          Ok,..i have the OEM 4 into 2/2 into 1s, how ever you want to call it,(bullet style,tapered ends and fixed baffle.
          I just bought 4 (EMGO) brand pods. Chrome end,washable and yes,..VERY un-restrictive.
          I have not done a thing with the carbs but replace the O-rings and clean them. Is there any way i can richen the mix with-out re-jetting? or is it a done deal?
          I am not looking to make this bike a monster, but i guess i want what most people want,(a smoothe running bike that can be enjoyable to run)

            Comment

            • TheCafeKid
              #4
              Originally posted by solarplex
              CafeKid,
              Thanks for such a fast response. I have not run this bike much,..just enough to get it to temp. once.
              Ok,..i have the OEM 4 into 2/2 into 1s, how ever you want to call it,(bullet style,tapered ends and fixed baffle.
              I just bought 4 (EMGO) brand pods. Chrome end,washable and yes,..VERY un-restrictive.
              I have not done a thing with the carbs but replace the O-rings and clean them. Is there any way i can richen the mix with-out re-jetting? or is it a done deal?
              I am not looking to make this bike a monster, but i guess i want what most people want,(a smoothe running bike that can be enjoyable to run)

              Sent ya a PM on some stuff bro... More than happy to help, and i have gone thru this stuff in multiple ways on THIS particular bike, which is a tad different than the 78 and 79 bikes. Check it out, and ask any questions you wish. Im at work at the moment, so it may take me a lil while to get back to you...But decisively a rejet is absolutely necessary in this situation. I gave you a few options to mill over, including going back to stock, which would need no rejet...

                Comment

                • solarplex
                  #5
                  CafeKid,
                  Many thanks again. Yes,..ill set the valves up to spec(hope my Clymers is correct) and ill get back to ya. Maybe then you can give me an Idea on what jetting #s i need to look for and where i can get them. I want to keep the 4 into 2s. maybe drill the baffle plate a bit but keep the pipes. I sort of like the twin pipe look on this bike.
                  Ill try to post fotos of it. I shortened the tail,welded new frnder mounts,lowered the fork and put clip-ons on it. Should be a fun bike. It is dark gray(high gloss). polishing the fork tube,tripple and engine. Keepin the chrome fender.

                    Comment

                    • dardoonk
                      Forum Sage
                      • Nov 2006
                      • 1002
                      • Indian Trail (Charlotte) NC
                      #6
                      solarplex,

                      Your in NEPA - assume that's northeast Pennsylvania, right? Let us know what town too, you'll be surprised how friendly everyone is here & it's not uncommon for guys local to one another to pitch in helping one another.
                      I've got a 77 GS750 as well. Unfortunately, I won't be much help on the specific jetting as I have 29mm smoothbores, but there are plenty of carb guru's on here that can give much better advice than myself.

                      You mention new O-rings... just to be clear, did you replace the O-rings between the head & manifold boots? I learned the hard way, and can tell you you might as well just do it now. Get them here :http://www.cycleorings.com/ It's a jetting nightmare if you don't.

                      I would go ahead and check your ignition timing as well now. If you are running stock ignition, you might want to get a tune up kit. Sounds to me like you might be struggling with poor advance or intermittent spark.

                      Keep us posted and Welcome Aboard GSR.

                      Kurt

                        Comment

                        • TheCafeKid
                          #7
                          Originally posted by dardoonk
                          solarplex,

                          Your in NEPA - assume that's northeast Pennsylvania, right? Let us know what town too, you'll be surprised how friendly everyone is here & it's not uncommon for guys local to one another to pitch in helping one another.
                          I've got a 77 GS750 as well. Unfortunately, I won't be much help on the specific jetting as I have 29mm smoothbores, but there are plenty of carb guru's on here that can give much better advice than myself.

                          You mention new O-rings... just to be clear, did you replace the O-rings between the head & manifold boots? I learned the hard way, and can tell you you might as well just do it now. Get them here :http://www.cycleorings.com/ It's a jetting nightmare if you don't.

                          I would go ahead and check your ignition timing as well now. If you are running stock ignition, you might want to get a tune up kit. Sounds to me like you might be struggling with poor advance or intermittent spark.

                          Keep us posted and Welcome Aboard GSR.

                          Kurt
                          Good points as well Kurt, and certainly things to check! But first things first, before you bother with any of that stuff, you'll be chasing your tail if you havent assured your valve clearances are in spec

                            Comment

                            • solarplex
                              #8
                              Uploaded PICS today

                              Thanks guys,...i live just north of Scranton,Pa.(unfortunately)..lol.
                              Here are some fotos for everyone to see my novice work. I have (not in current foto after paint job) 300mm clip-ons and pod filters. they are on the bike now.,...........Shannon

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