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    Please Help Jet my GS for Open Exhaust

    I've searched but haven't found info I'm looking for here.
    So i have rebuilt the carbs with spec jets (cant recall size) on my '82 GS650 GLZ BUT have now chosen to go a different direction with this build and Bobbify. I have [basically open] Reinhart exhaust and the original airbox with foam filter. Please help me calculate the jets and give me all the recommended settings to tune properly for this setup at sea level (Canadaian west coast eh). It starts and warms up with choke fine and revs fine sitting but after about 20-30 seconds riding it starts to die then dies. It will start again (barely) with choke but hates running again. I then hit the highway to give 'er heck but it pops, farts and feels like its running on 1 cylinder Then dies again. DUH, I says to myself - jetting.

    Thanks guys n Gals,
    Trev
    Last edited by Canadian Eh; 04-14-2022, 09:43 AM.
    ~~o&o>
    ... from a free frame and wheels and box of parts to a rideable wreck is better than a slap in the belly with a dead salmon anyday eh

    #2
    Post this in the Carb subforum
    1978 GS 1000 (since new)
    1979 GS 1000 (The Fridge, superbike replica project)
    1978 GS 1000 (parts)
    1981 GS 850 (anyone want a project?)
    1981 GPZ 550 (backroad screamer)
    1970 450 Mk IIID (THUMP!)
    2007 DRz 400S
    1999 ATK 490ES
    1994 DR 350SES

    Comment


      #3
      Doesn't sound like an actual jetting issue although with the open pipe you should increase the main jet a size or two but running slightly lean won't cause the problem you are having.
      It sounds like you are having fuel supply issues which may be fuel tap , kinked fuel hose or float height related etc.
      If this only arose after having the carbs apart then something done there or incorrectly assembled is most likely the cause.
      Mikuni Viton Choke Plunger Seat Renewal.
      VITON Choke plunger seals .KAWASAKI Z1,Z900,Z650,Z1000,Z1R,SUZUKI GS1000,GSXR,RF | eBay

      Air Corrector Jets for Mikuni VM 24, 26 and 28mm carbs .
      https://www.ebay.co.uk/itm/254380193...84.m1555.l2649



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      Comment


        #4
        Originally posted by zed1015 View Post
        Doesn't sound like an actual jetting issue although with the open pipe you should increase the main jet a size or two but running slightly lean won't cause the problem you are having.
        It sounds like you are having fuel supply issues which may be fuel tap , kinked fuel hose or float height related etc.
        If this only arose after having the carbs apart then something done there or incorrectly assembled is most likely the cause.
        Thanks, I agree its something fuel related for sure. By fuel tap I suspect you mean the petcock? Ijust put a new OEM one on so I doubt thats it. Float height and jets is what I'll have to work on next. I really appreciate the reply!
        ~~o&o>
        ... from a free frame and wheels and box of parts to a rideable wreck is better than a slap in the belly with a dead salmon anyday eh

        Comment


          #5
          When was the last time you checked the valves?
          Expecting the Spanish Inquisition
          1981 GS850G: the Ratzuki
          1981 GS1100E

          Comment


            #6
            Originally posted by zuluwiz View Post
            When was the last time you checked the valves?
            I recently had a bike mechanic shim the valves so they've been checked.
            cheers
            ~~o&o>
            ... from a free frame and wheels and box of parts to a rideable wreck is better than a slap in the belly with a dead salmon anyday eh

            Comment


              #7
              Originally posted by zed1015 View Post
              Doesn't sound like an actual jetting issue although with the open pipe you should increase the main jet a size or two but running slightly lean won't cause the problem you are having.
              It sounds like you are having fuel supply issues which may be fuel tap , kinked fuel hose or float height related etc.
              If this only arose after having the carbs apart then something done there or incorrectly assembled is most likely the cause.
              All fuel issues have been checked and remedied. New Petcock, no kinked lines, float heights adjusted and a dynojet kit installed. Issue persists.
              Is there any possibility there is an electrical issue that only shows an issue when you get riding? - ie you idle and rev fine but get out on the road and it starts bagging. Mechanic isnstumped and wants to try a different cdi ignitor. I have no idea
              ~~o&o>
              ... from a free frame and wheels and box of parts to a rideable wreck is better than a slap in the belly with a dead salmon anyday eh

              Comment


                #8
                Originally posted by Canadian Eh View Post

                Mechanic isnstumped and wants to try a different cdi ignitor. I have no idea
                If your "mechanic" wants to try a different "CDI", you need a new mechanic. That bike never had a CDI.

                Also, be warned that there are some on the forum that will not give any support after you mention "open exhaust". They might mention how socially irresponsible it is, and then not give any further support, or they will just ignore any other requests you might have. I sort of agree with them about loud exhaust, but I will mention that with a stock airbox, you might not need to re-jet. Maybe one size up, maybe none at all.

                Comment


                  #9
                  Make sure your tank is venting.
                  1981 GS1100E

                  Comment


                    #10
                    Originally posted by bull958 View Post
                    Make sure your tank is venting.
                    I was thinking the same. Easy enough to check. Run the bike w/ the gas cap off. Of course you don't want a lot of fuel in the tank for this exercise. If the dying-in-20-30-seconds-of-riding goes away, rebuild or replace your gas cap, as it isn't venting.
                    Rich
                    1982 GS 750TZ
                    2015 Triumph Tiger 1200

                    BikeCliff's / Charging System Sorted / Posting Pics
                    Destroy-Rebuild 750T/ Destroy-Rebuild part deux

                    Comment


                      #11
                      Vent is sure something to check out, but really wouldn't think the tank not venting could cause a problem within 20 or 30 sec. Easy to check to know for sure.
                      1983 GS1100E, 1983 CB1100F, 1991 GSX1100G, 1996 Kaw. ZL600 Eliminator, 1999 Bandit 1200S, 2005 Bandit 1200S, 2000 Kaw. ZRX 1100

                      Comment


                        #12
                        I would suspect air leaks around your airbox or at the boots where it joins the cards or the intake boot O rings. If you still have the original airbox then the jetting changes for an exhaust are not that big (not enough to cause what you are talking about).

                        Did you oil the foam filter? Running it dry might lean it out enough to cause those issues I guess.....

                        For the pipe just go up a step (5) on the main jet and raise the needle one notch (I believe it's still adjustable needles in Canada) then tune the air corrector screw 2.5-3 turns out from lightly seated most likely.
                        1980 GS1000G - Sold
                        1978 GS1000E - Finished!
                        1980 GS550E - Fixed & given to a friend
                        1983 GS750ES Special - Sold
                        2009 KLR 650 - Sold - gone to TX!
                        1982 GS1100G - Rebuilt and finished. - Sold
                        2009 TE610 - Dual Sporting around dreaming of Dakar.....

                        www.parasiticsanalytics.com

                        TWINPOT BRAKE UPGRADE LINKY: http://www.thegsresources.com/_forum...e-on-78-Skunk/

                        Comment


                          #13
                          Hi all. THANK YOU for your replies. I will let you know what has been happening since you replied - I haven't checked back in a long time.
                          Since 2 mechanics have suggested that dynojetting would fix the problem i bought a kit and installed to no avail. Since THAT waste of time, I have found the Suzuki GS Guru locally who said I could pick his brain all I want. Just as a couple of you have mentioned, he mentioned gas cap venting but also said the stock beige coils are garbage and have been an issue since the bikes were young. I just ordered new (green) 3ohm Dynatek coils so will install them soon and let you know how those 2 things help.
                          ~~o&o>
                          ... from a free frame and wheels and box of parts to a rideable wreck is better than a slap in the belly with a dead salmon anyday eh

                          Comment


                            #14
                            Well, I guess I've been lucky, never a problem from a stock Suzuki coil. Have a set of Accell on my GS1100E that was there when I bought it, and wish it still had the OEM.,
                            1983 GS1100E, 1983 CB1100F, 1991 GSX1100G, 1996 Kaw. ZL600 Eliminator, 1999 Bandit 1200S, 2005 Bandit 1200S, 2000 Kaw. ZRX 1100

                            Comment


                              #15
                              Originally posted by salty_monk View Post
                              I would suspect air leaks around your airbox or at the boots where it joins the cards or the intake boot O rings. If you still have the original airbox then the jetting changes for an exhaust are not that big (not enough to cause what you are talking about).

                              Did you oil the foam filter? Running it dry might lean it out enough to cause those issues I guess.....

                              For the pipe just go up a step (5) on the main jet and raise the needle one notch (I believe it's still adjustable needles in Canada) then tune the air corrector screw 2.5-3 turns out from lightly seated most likely.
                              It is a new air filter that was pre-oiled and I have brand new boots that connect to the carbs. Thanks for the set-up tips
                              ~~o&o>
                              ... from a free frame and wheels and box of parts to a rideable wreck is better than a slap in the belly with a dead salmon anyday eh

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