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Carb Issues (hopefully)

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  • Carb Issues (hopefully)

    OK so this may get a little long winded but i will try and keep it short.
    So i see an advert for a 1995 suzuki gsx600f on ebay.
    went to view it and all seemed well.
    struck a deal and the guy agreed to deliver it to my address as i have not yet sorted out insurance etc.

    got it delivered the next day now i will list the problems.
    pushed it into my garage and left it as i had work and had to dash.

    next day i go into garage start it up and its running like a bag of sh*t!!

    so i have a lopl over it and one of the vacuum port rubber caps is missing, i thought BINGO (easy fix) NOPE............

    so i thought ok clean the carbs re-sync them etc etc.


    so after i start taking things apart this is where more problems than i dont know what start propping up.

    1. firstly there was rust coloured sediment in the float bowls so all the carbs got stripped down and thoroughly cleaned in an ultrasonic bath plus carb cleaner plus blown out with compressor etc etc.
    i then thought well that sediment has to be coming from somewhere but suprisingly the tank looks mint for 21 years old but none the less it got emptied and lined.
    2. all the main jets are stock sizes 110 here in the UK.
    3. i put it all back together and fired it up ( or tried too)
    if i put the choke on it will rev to high hell and if i take the choke off it will die i then adjust the idle screw ever so slightly and it revs to high hell again.
    4. ive bench synced the carbs with the best of accuracy and then tried syncing them with my carbtune but the idle is that bad i cant even get a bloody reading.
    5. im at my witsend.
    6. i have replaced all plugs and HT leads as i got them on a good deal so thought why not.
    7. Oil has been replaced along with filter.
    8. Valves have been checked and shims adjusted where necessary (mainly intake)
    9. discover oil all over the place and turns out the o ring for the alternator is bust so i replace that.
    10. i have adjusted all float heights to the correct spec
    11. today i discover what i think may be an air leak on the carb to inlet manifold rubber boots.
    12 when i go to remove the oil lines from ontop the hex heads have rounded off.


    is there a possibility that what seems like a really small air leak can cause so much trouble?
    ive had air leaks before on previous bikes and they have never caused this amount of trouble.

    sorry for the long winded post but if anyone has had any similar trouble please let me know


  • #2
    Definitely sounds like an air leak. The fact that the carbs are out of sync is probably magnifying that. Fix any air leaks, and you should be able to start syncing. I've found several rounds are required the first time after rebuilding carbs. (set idle speed to 1750 sync, readjust to 1750, sync, readjust rinse, repeat etc)good luck with the rounded off Allens, my guess is the PO didn't have the right size metric set and just used SAE...
    1998 Katana 750
    1992 Katana 1100
    2006 Ninja 250

    2006 Katana 600 RIP - 130k miles


    • #3
      so i have replaced the o ring's on the intake boots, i have bench synced the carbs again, put it all back together, fresh fuel, tightened everything up and still the same problem, i have synced the carbs (using a carbtune proII)
      and still when i turn it on the engine will idle around 700RPM and if i increase the idle it revs straight up to 4000RPM and if i give it a little throttle (and i mean a a tiny amount) it revs to around 4000RPM. i have had it running and sprayed carb cleaner around all the intake boots both post and pre carb with no effect so im confident there are no more air leaks.

      ive worked on quite a good amount of bikes in the past few years and never had a problem like this where i have not been able to find the issue. I know its going to be one hell of a rewarding experience once i get to the bottom of this and im fairly confident on working on any aspect of the bike.

      BUT i wonder if anyone else has had this sort of problem with the 600

      thanks for helping


      • #4
        Anything above 3000 rpm is a linkage or choke issue. Stuck plungers, cable bind, throttle linkage bind on the carb3 carb boot clamp has happened.
        "I'm sorry, I didn't mean to upset you when I called you stupid. I thought you already knew..."
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        • #5
          Still sounds like an air leak. Couple places you might not have checked - the vacum caps that cover the sync ports can crack as they get old and dry, need all 3 present and in good shape. The carb caps themselves - if something isn't tightened down enough...air leak. If something was overtightened, the cap might have warped. Or maybe it got scraped when you had things apart, and now there's a ridge/groove. Sanding on a plane of glass can smooth that out if it exists. Drain tube from the airbox needs to be capped, and cap in good condition. Tube has to be in good condition with no cracks.

          Do you have a CA smog equipped bike? If so, all that tubing has to be checked for cracks. If you converted it from CA to 49 state, check where you plugged the vent lines at the bottom of the carbs.

          There's probably one or two more (or 8) possibilities as fas as air leaks go, need to be super duper thorough.

          If that all checks out, one more thing to check is your clamps holding the intake boots to the head - is one of them (#3 I believe) interfering with the throttle fully closing?

          And last but not least, your pilot circuts may still be dirty and it just idles like poo becuase of that. Some people with really bad carbs have had to soak them multiple times. I like to run fishing line (NOT wire!!!) Through the jet orifices and the pilot circuit channels. After a 3 day chem dip soak, I still had total blockage on 1 channel I never would have known about otherwise.
          1998 Katana 750
          1992 Katana 1100
          2006 Ninja 250

          2006 Katana 600 RIP - 130k miles


          • #6
            Originally posted by shpielers View Post
            I like to run fishing line (NOT wire!!!) Through the jet orifices and the pilot circuit channels. After a 3 day chem dip soak, I still had total blockage on 1 channel I never would have known about otherwise.
            I'm honestly not a fan of this method. I blow them out with a compressor. Just a little compressor, nothing fancy. I hold them up in the direction of the light. If I see light, and they look right, awesome. If not, they go back in the Berrymans Chemdip. It's taken up to 4 days before, but it always works.

            You mean blockage as in the circuit in the carburetor body? I never have that problem.
            Last edited by arsenic; 09-14-2016, 02:14 AM.


            • #7
              Yep, blockage there. Really gooey junk. If I had a compressor, I'd certainly have given that a try, but the cans of compressed air you can buy for cleaning keyboards didn't do the trick. (this was on an 1100 btw, in case that makes a difference.) I stuck it back in the dip after that for another day.

              Compressor certainly sounds faster/easier. Someday I'll have a garage and then oh the tools I can buy...
              1998 Katana 750
              1992 Katana 1100
              2006 Ninja 250

              2006 Katana 600 RIP - 130k miles


              • #8
                thanks for all the reply's its really appreciated.
                Im in the UK so we dont have the SMOG Equipped bikes.
                Going to go back over the carbs tomorrow and triple check the lot
                will let you know how it goes


                • #9
                  You seems to have a pretty good idea what you're doing, so I can't offer you any pointers. Good luck.


                  • #10
                    There are orings under the black caps at the vacuum sync ports as well. Check those. Number 3 carb clamp interferes with choke as mentioned. Make sure all the plungers rise and fall smoothly. Make sure the springs are on there correctly. If they bind up they don't push them back down so well. I can't say I've ever heard this happen but it might be a good idea to suck on the vacuum hose from carb 4 to the petcock to make sure the diaphragm in the petcock isn't blown out. If u can suck air, that would be a major air leak. Check ur oil for fuel. If the carbs are dumping fuel into the head it would lead to a crazy idle.

                    You could also check spark plugs for an indication to narrow down the issue, or check the header temps. If one is way cooler or way hotter than the rest that also would be good place to start
                    Last edited by maniac1886; 09-14-2016, 04:06 PM.
                    My build thread (Black Betty) '97 600 (Dearly Departed)
                    2007 GSXR 750


                    • #11
                      When you adjusted the carbs, make sure you were using the right specs for the bike model. UK specific models will have different settings than US models. For example, in the US ... 2.5 turns on the A/F screws is pretty much required. It's closer to 1.5 turns on the UK specific models. check/confirm and adjust accordingly.

                      You sound like you know what your doing, but we all make some over sites sometime, so don't take this the wrong way.... but. Did you make sure the idle adjustment cable was 100% backed out when you did the bench sync? Also check that none of the butterflies are sticking to the sides holding the carbs partially open. They should not click when opening /closing and should snap fully closed, no pressure or catching when opened back up. Best to check this with out throttle cable attached.

                      Try running the bike with the air box off temporarily and check slides are not sticking up, equally moving, and the butterflies are fully closing when your not adding throttle. Also check all 4 of the "choke" plungers are working in conjunction and fully closing when turning it off.

                      Also as mentioned, the carb boot clamps tend to get in the way of the throttle or choke cables and will cause them to hang. Make sure those are no where near those. Turn them so the screw head is facing up, 1-2 on the left side, 3-4 on the right side. That leaves the screw section of the clamps no where near the throttle assembly.

                      Oh, one last thing. Mentioned was the small orings under the sync ports on the caps. Additionally I have found the cap castings many times are not properly cleaned, and cause leaks around the caps. I use fine grit sand paper on a flat surface to make sure the cap bottoms are 100% flat for a good seal. Doesn't take much, and after the first couple of swipes you can look to see if the cap was flat or not.

                      Last edited by Kreylyn; 09-16-2016, 10:02 AM.
                      93 750 Kat

                      Modified Swingarm, 5.5 GSXR Rear with 180/55 and 520 Chain, 750 to 600 Tail conversion, more to come. Long Term Project build thread

                      "I've done this a thousand times before. What could possibly go wron.... Ooops!"