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01 Kat 600 hesitating about 5500-6000 RPM - Updated

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  • 01 Kat 600 hesitating about 5500-6000 RPM - Updated

    I took my bike into the shop a couple weeks ago, got the carbs synch'd, then changed the oil and went out for a nice ride. I noticed that when i was cruising in top gear and pulling about 5500-6000 RPM's the bike would hesitate when giving it gas. If i ducked down on the tank it got worse, would lurch when trying to keep a steady speed. If I was in a lower gear the problem didn't occur. If I stayed in 6th and got past 6000 it was smooth.

    I pulled the tank off last night to see if there was anything obviously not right and check the plugs.

    One thing i noticed, there are two rubber hoses on the airbox side of the carbs, one connects to the petcock, and the other was dangling loose, but the end was expanded as though it was connected to something at some time.

    EDIT: I also noticed a hose on the engine side of the carbs, what should that be connected to?

    Also got a pic of the spark plug, it has about 2000 miles on it

    Suggestions on what could be going on?

    And for anyone interested there was some Mutal of Omaha stuff going on right next to me while i was dissasembling the bike


    I just went and looked around some more and pulled some plastics off and found another hose! From the look and bend of this one it should be connected to the drain in the center of the tank. So now I'm left wondering where do all the rest of these hoses go?!

    I have two hoses on the airbox side of the carbs between carbs 1 and 2 and another between 3 and 4. There is also a hose on the engine side of carb 4 (left) the connector where this is connected is plugged on all the other carbs.

    here's a pic of what i'm looking at. Thanks again for all your help, the Kat's going on the dyno tomorrow so hopefully this can all get sorted out before then.

    2001 Katana 600
    1998 Jeep TJ 4.0
    2005 Subaru Impreza STi

  • #2
    The one that is dangling loose might be the one that connects to the bottom of ur tank. I think its like a breather hose or something, it should connect somewhere on the bottom in the middle of ur tank, right to the right of the petcock. On my bike I have 3 hoses,
    1. connects to the petcock for gas
    2. this one alos connects to the petcock, but it is for vacuum
    3. breather tube, goes to bottom of tank

    Hope that helps


    • #3
      i like grapes!!
      Lean in Lean out.
      1993 GSX750F Katana SOLD
      2002 GSX750R Black. SOLD
      2000 TL1000RR silver, SOLD
      2000 yamaha R1 red katana



      • #4
        Originally posted by xbubbax
        i like grapes!!
        Glad you like grapes, do they help with Katana hesitation?

        Updated the above for new info

        Thanks again
        2001 Katana 600
        1998 Jeep TJ 4.0
        2005 Subaru Impreza STi


        • #5
          Re: 01 Kat 600 hesitating about 5500-6000 RPM - Updated

          Hoses labeled (in your pic) from Carbs 1 & 2 and from Carbs 3 & 4 run across the top of the airbox to the little brackets by the air filter opening and just hang there. They allow the carbs to displace air and draw in air as the fuel level rises and falls, plus provide a spare drain for the fuel rail if the bike falls over (less fuel going into the engine oil).

          Hose labeled drain hose goes to the center underside of the tank, and has three functions:
          (A) overflow hose if you overfill your tank;
          (B) drain line for rain water that gets in your gas cap surround
          (C) air vent to displace fuel consumed while riding.

          Hose labeled From Carb 4 goes to the back of the petcock, to permit vaccum to open the petcock in ON and RES positions (defeated in PRIME).

          Fuel line goes to the side-nozzle on the petcock, and supplies fuel to the carbs.

          Best guesses as to the other problems:
          Carb #3: float stuck or jets clogged, missing vacuum cap, or took in some water. Either way, carb #3 not fueling correctly. I noticed in your pic above that the cap for carb #3 looks much cleaner than the others -- why? Did someone already get into it?
          spark plug wire/spark plug boot to plug #3 defective or not seated correctly.
          Choke cable damaged and sticking (notice the wear marks on the cross-bar over the valve covers -- indicates it was trapped between the tank and the bar, taking abuse by being beaten from above). See for more details on this...

          I agree that you should check your tank for the presence of rust; your carbs as well (will appear as an orange paste in the bottom of the carb bowls that looks zero like rust on initial inspection).

          Good Luck!
          =-= The CyberPoet
          Remember The CyberPoet


          • #6
            Thanks for all the help, I just got back from a test ride, when i got the bike back from the shop, the vacuum line was connected to the tank drain, and the 1/2 air line was connected to the petcock. Got everything connected properly and it's running like a top! no hesitation, smooth acceleration through all RPM ranges.

            The top of carb3 has always been cleaner since i got the bike last year. The only work that i know of that has been done is having them synch'd a couple weeks ago.

            Thanks for the link about the clutch cable, I'll tackle that when I run this tank of gas down. I've looked in the tank for rust, being a fellow Gulf Coaster I've had my battles with rusty gas tanks Haven't found any in the tank, fuel filter, or anywhere else on the bike.
            2001 Katana 600
            1998 Jeep TJ 4.0
            2005 Subaru Impreza STi