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Help!! mid range carb issue

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  • Help!! mid range carb issue

    I have a 78 xs11. I am using a uni brand air filter (new). The problem is when I ride it and open it up at 2500 RPM it will reach 4000 RPM and studder the engine wont gain more RPM. Now if I stop take off the bottom of the airbox with the filter. The thing will take off like a cat shot in the butt with a BB gun.

    The carbs have 142.5 pilots 145 mains needle clip middle slot.

    The exhaust is stock head pipes with HD Dyna Glide mufflers.

    If anyone is running HD mufflers please post/reply with the jets and needle clip position you are running and type of airfilter. I have been wrestling with this problem since the begining of spring. This is my first xs1100 but, I have owned and repaired countless bikes. I have never ran into this type of problem before.

  • #2
    Welcome to the site...

    With the information you have given its too hard to point our fingers at one single reason. So, here come the questions...

    Do you have UNI Pods or are you using the stock air box? You said filter and not filters so I will assume your using the stock air box...

    I assume you made a tyop and your pilots are 42.5 and not 145.5...anycase, why are you running these size jets?

    Stock for the 78 had 45 pilots and 137.5 mains. The only reason to change those are if your have made considerable changes to the air box or the exhaust...

    Also, when is the last time you cleaned the carbs and how through of a job did you do?

    Take a look at the tech tips for carb cleaning and you might notice a few things that come apart that you missed..?

    Just adding the HD mufflers alone do not warrent the changes made to the jet sizes. I cant think of any reason you would have to go larger than 140 mains with your setup.

    What color are your plugs, are they showing a rich condition? Taking off the bottom of the air box kinda proves that the engine needs more air and less fuel. IMO you need to try some 137.5 mains, first check your plug color to verify its too rich...
    Last edited by WMarshy; 07-15-2010, 09:27 AM.
    '79 XS11 F
    Stock except K&N

    '79 XS11 SF
    Stock, no title.

    '84 Chevy K-10 "Big Blue"
    GM 350, Muncie SM465, NP208, GM 10 Bolt with 3.42gears turnin 31x10.5 Baja Claws

    "What they do have is an implacable, unrelenting presence and movement that bespeaks massive power lurking behind paint and chrome. They don't wail like a screeching ninja, the don't rumble like a harley. They just growl like a spactic, stressed out badger waiting to rip your face off and eat your soul." Trainzz~RIP~

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    • #3
      If you pull the air box and it runs right, it's an indication that your jetting is too fat, like Marshy said. I've seen them hit a wall in the 4-5k range from being over-rich. You could either drop back down on your jet size, or open up the intake. A free flowing filter and drilled air box might put you in the correct range. If you don't have a colortune plug, now would be a good time to get one - they come in very handy when trying to get your jetting right. JAT
      I think I have a loose screw behind the handlebars.

      '79 XS11 Standard, Jardine 4/1, Dyna DC1-1 Coils, 145 mains, 45 pilots, plastic floats - 25.7mm, XV920 fuel valves, inline fuel filters, speed bleeders, Mikes XS pods, spade-type fuse block, fork brace, progressive fork springs/shocks, manual petcocks, 750 FD, Venture cam chain tensioner, SS brake lines

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      • #4
        as the others have said,
        sounds like your running rich,
        make sure you havent got any restrictions
        in the air box or snorkel,
        also make sure the carb vent hoses arent blocked or restricted,
        check your float heights arent to rich and you could drop the
        size of you main jets back to stock,
        youll need to clean your spark plugs
        if theyve been fouled.
        pete


        new owner of
        08 gen2 hayabusa


        former owner
        1981 xs1100 RH (aus) (5N5)
        zrx carbs
        18mm float height
        145 main jets
        38 pilots
        slide needle shimmed .5mm washer
        fitted with v/stax and uni pod filters

        [url]http://www.youtube.com/watch?v=3pA8dwxmAVA&feature=mfu_in_order&list=UL[/url]

        Comment


        • #5
          Carb issues

          Thank you all you have been very informative. I will be trying you advice this weekend. I will post after that to let you guys know what happened. Until then I will just have to commute on my 76' xs650 hard tail bobber. You guys all keep the rubber side down.

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          • #6
            here is what i had to do to cure some of my issues..

            How to make HD pipes work on a xs1100.doc
            http://www.megaupload.com/?d=SV97O793

            no... i'm not done yet so don't ask about jetting...
            i'm still fine tuning that.
            1979 XS1100SF Special.78 E motor/carbs, Jardine 4-2 exhaust, XS Green coils, Corbin seat, S.S. Brake lines, Hard cases, Heated grips.

            2012 FJR1300 Gen 2. Heli bar risers, R-gaza crash bars, mccruise cruise control.

            (2)2008 WR250R. Because kids outgrew others.

            2007 Suzuki V-Strom 1000. (Just added 2024) pre-crashed.

            1975 Kawasaki S1 250. My first bike. Still have it. NO I'm not selling it!!

            Most bike problems are caused by a loose nut connecting the handlebars and the seat!!

            Comment


            • #7
              Hd muffs and Pods

              Hi

              On my MNS with the late carbs I am using the standard 110s and the 42.5 pilots, these are what are stock with the bike. The needle is non adjustable. I do have a very high rpm burple at 7000 rpm, but I only ran it at that speed as a test, never get there other wise, you know, getting old. The muffs are the sportys smaller ones, 19 inches long, and pictured in the above download for jetting sportys muffs . The pods are the emgo cheapo brand that I got from Georgefix. I didnt have any luck with easily removing my air box, so I set it aside and George concurred that the pods eliminate all the effort, now I can take the carbs off in ten minutes flat if I need to.
              Last edited by tadtl1; 08-04-2010, 09:39 PM.
              80 MNS , Georgefix pods , crossed fuel lines, no octy, inline filters, Daytona handlebar, custom seat, Hardley 19 muffs

              Comment


              • #8
                Carbs off

                I am about to make a movie that shows how to remove and install the carbs with the airbox, probably in 10 mins or less.
                You can't stay young forever, but you can be immature for the rest of your life...

                '78E "Pathfinder" Show bike...
                Lovingly restored by Dave Delzell
                Drilled airbox
                Tkat fork brace
                Hardly mufflers
                late model carbs
                Newer style fuses
                Oil pressure guage
                Custom security system
                Stainless braid brake lines

                Comment


                • #9
                  Originally posted by planedick View Post
                  I am about to make a movie that shows how to remove and install the carbs with the airbox, probably in 10 mins or less.
                  That I want to see.
                  Nathan
                  KD9ARL

                  μολὼν λαβέ

                  1978 XS1100E
                  K&N Filter
                  #45 pilot Jet, #137.5 Main Jet
                  OEM Exhaust
                  ATK Fork Brace
                  LED Dash lights
                  Ammeter, Oil Pressure, Oil Temp, and Volt Meters

                  Green Monster Coils
                  SS Brake Lines
                  Vision 550 Auto Tensioner

                  In any moment of decision the best thing you can do is the right thing, the next best thing is the wrong thing, and the worst thing you can do is nothing.

                  Theodore Roosevelt

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                  • #10
                    Originally posted by natemoen View Post
                    That I want to see.
                    Ditto. I would be interested in seeing this. A number of years back when I was heavy in to the carb removal/carb install phase, I was getting pretty good, but I don't think I ever got to 10 minutes. Heck, it takes me that long to get the necessary tools ready for action!

                    The pressure is on!
                    Ken Talbot

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