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no throttle response, especially when cold.

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  • no throttle response, especially when cold.

    i have a 99 katana 600 and i am trying to sync the carbs. the only problem is I can't get a good reading on my gauges, they just go crazy. if I disconnect the hose and put my finger on it I can feel the vacuum pulsing really quick instead of a steady vacuum. I have sprayed carb spray to check for leaks but I can't find any. Is there something I am doing wrong? Also, I tried a different set of gauges and i get the same results.Please help!!!!

  • #2
    You will not get constant vacuum...
    Not untill 10000000000rpm...

    Are you using murcury? Or gauges?
    If Murcury type make sure you have the little restrictors in the tubes..

    If gauges then you need to adjust the needle valves..
    No needle valve? oops then you need restrictors in the tubes of them too..

    More information please.......

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    • #3
      I am using gauges and I do have the adjustable valves in line with the gauges. If I adjust the valves the best stable reading I can get is about
      2-4 inches of vacuum. I have used two different sets of gauges with the same results. Both sets are pretty old so is it possible the are both bad. Note: I am syncing the carbs because I have poor throttle response under 6k rpm and no throttle response unless the bike has ran for at least five minutes.

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      • #4
        Sounds like you need a known working tool for this job...

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        • #5
          Let the beast warm up all the way (15 minutes of running).
          Set the idle to 1800 RPM (artificially high idle) using the idle thumbwheel.
          Take your readings and use the sync adjustments to balance 1 to 2, then 4 to 3, and finally 1&2 to 3 & 4. If the needles vary over a range (as they will), compare the ranges. Since you are using a questionable set of gauges, compare values from a single cylinder on all the different gauges and compensate as needed (if needed). It's not important that they all read the right number -- just that they all read the same relative to each other.

          Cheers
          =-= The CyberPoet
          Remember The CyberPoet

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          • #6
            SO your not using one of these?
            http://www.carbtune.com/

            why bother?

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            • #7
              Originally posted by donmega
              SO your not using one of these?
              http://www.carbtune.com/

              why bother?
              If you're talking to me, yes, I use a Morgan CarbTuneII. But not everyone has the $$ to buy one readily...

              Cheers
              =-= The CyberPoet
              Remember The CyberPoet

              Comment


              • #8
                Nah it was for the original poster, if you cant afford one then I wouldnt even bother or call around to see what a shop would charge.

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                • #9
                  I think i figured it out. I switched around the vacuum hoses that go to the gauges so the valves are going the opposite way(i'm not sure if this helped but it seemed like more air was able to pass one way than the other). I then started to adjust the screw between carb 3&4 and I was able to get a steady vacuum reading of about 15 inches of vacuum on carb #4. I will adjust the others and see what happens. I think my carbs were just so far out of whack that I wasn't getting a good reading. I also work with a guy that has a carbtune so I will try to borrow it and fine tune the carbs later.

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                  • #10
                    ok. i finally got the carbs synced but my original problem still exists. the problem is that it has poor throttle response especially when it is cold. when i first start the bike i have to leave it choked for about 5-6 minutes at 3k rpm or else it will die when i go to give it gas. once it warms up it will no longer die but it still has crappy throttle response( and it bogs down a bit if I twist the throttle real quick). so far i have put new plugs in it, cleaned and synced the carbs and ran a fuel system cleaner. It also has a slight rough idle when warmed up and i can't adjust my idle past about 1100 rpm and sometimes my idle will even stick at 2k rpm. this thing seems to have a mind of its own, any ideas?

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                    • #11
                      Q: does it have a jetkit in it, or are the carbs still stock?

                      A: Quite running the choke for more than 30 to 60 seconds; after that, if it still needs a hand, use the throttle instead or set your idle speed higher (idle thumbscrew, left fairing opening by your knee). Using the choke for more than a minute really loads your plugs up with fouling (which burns off once it gets to full temp); running choke that long can foul the plugs in a matter of starts, not hundreds of miles.

                      Q: Have you check the air filter?
                      Q: How long are you letting warm up after you shut the choke off?

                      Cheers
                      =-= The CyberPoet
                      Remember The CyberPoet

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                      • #12
                        i can't turn my idle up past 1100rpm because the thumbwheel is turned all the way up. it was like this ever since i bought it. also my idle will stick around 2k rpm every once in a while. the bike is completely stock

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                        • #13
                          well, you idle sticking at 2k means that it either has sticking throttle cable(s), or that there is still dried fuel residues or other contaminants in the narrower passages of the carbs. If with the idle thumbwheel turned all the way up, you're still idling too low, then it's time to dig into those carbs, because there are still issues -- that thumbwheel should be able to force them up to 1800 RPM without fail (as done for a sync).

                          Cheers
                          =-= The CyberPoet
                          Remember The CyberPoet

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