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Bike wants to rev-up holding the throttle steady??

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  • Bike wants to rev-up holding the throttle steady??

    I have been working on this XS11 SG for a few weeks now. I replaced the rings/valve seals, did a valve job. Replaced most of the valve shims to get the clearance right. Cleaned the carbs, mercury stick the carbs. It seemed to be running ok until I took it for a ride. It was running on three cylinder. The number four carb I figured was having problems. I replaced all the idle air screws/orings,etc. Set them up at about 2 1/2 turns. Cleaned the carb again.
    Put them back on the bike. Used the mercury stick again. They were off a little. Now the bike wants to rev-up holding the throttle steady. It seems to go away after the engine gets warm. It looks like the #4 cylinder is running now. Would the idle air screws cause the reving of the RPM's ? I need to spend more time on it but thought I would ask the experts on this great site.

    What does everyone think? It still seems to be carb related to me.

    Also I am having battery problems. It will not keep a charge. Not sure if it is a battery or charging problems. One battery cell on the outside left has like a white milky streak/cloud in it. I am thinking maybe it is bad. I was told it was fairy new.

    Thank guys.
    Bill
    1980 XS1100 SG
    Jardine Spaghetti with Harley Mufflers

  • #2
    If you just blindly set the idle mixture screw to 2.5 turns out then you didn't do a proper sync and idle mixture setup.

    You you have your sticks hooked up to the boots turn the idle mix screws in or out till you reach the highest vacuum possible on that cylinder. Then sync all the carbs again. Move to the next carb and adjust for highest vacuum on that cyclinder, sync and repeat that for the other carbs. And remember to have your idle set down low and keep adjusting it down through the process as it raises up throughout. Also, at this point having the idle mixture screws all at the same number of turns out doesn't matter. Most likely they will all be at a different spot.

    Do that a couple times and your carbs will be pretty close to perfectly synced and running like a top.
    Last edited by natemoen; 06-28-2015, 07:45 AM.
    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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    • #3
      Originally posted by natemoen View Post
      If you just blindly set the idle mixture screw to 2.5 turns out then you didn't do a proper sync and idle mixture setup.

      You you have your sticks hooked up to the boots turn the idle mix screws in or out till you reach the highest vacuum possible on that cylinder. Then sync all the carbs again. Move to the next carb and adjust for highest vacuum on that cyclinder, sync and repeat that for the other carbs. And remember to have your idle set down low and keep adjusting it down through the process as it raises up throughout. Also, at this point having the idle mixture screws all at the same number of turns out doesn't matter. Most likely they will all be at a different spot.

      Do that a couple times and your carbs will be pretty close to perfectly synced and running like a top.
      Thanks for the info. I will try this method. I tried to adjust the idle screws by listening until max rpm's for each carb.

      Bill
      1980 XS1100 SG
      Jardine Spaghetti with Harley Mufflers

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      • #4
        Before you used the manometer, did you do a proper bench sync? It's very important that you do.

        Easy Bench Sync Method
        Marty (in Mississippi)
        XS1100SG
        XS650SK
        XS650SH
        XS650G
        XS6502F
        XS650E

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        • #5
          It seems to be running OK now after re-synching the carbs. Now my problem is the battery and/or charging. How can you test for a bad cell? One cell has white/milky stuff in it. After charging all night it started right up this morning. After I took it for a 5-10 mile test drive and let it set for A COUPLE OF HOURS THE BATTERY SEEMS TO BE DOWN AGAIN. I use to have a electrode tester long time ago. Do they still use them to check for bad cells? I want to make sure my battery is good first before I do any debugging.

          Thanks everyone. I am getting closer to getting this girl running.

          Bill
          1980 XS1100 SG
          Jardine Spaghetti with Harley Mufflers

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