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Thread: Carb synchroniser unresponsive

  1. #1
    Member wheel_of_steell's Avatar
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    Carb synchroniser unresponsive

    So I'm syncing the carbs on my bandit 1200. The problem is, what I can hear is not matching what the gauges are telling me.

    1. I calibrated all the gauges first, by teeing them all into cylinder #4 and adjusting the hose pinch bolts to get the same output on all four gauges
    2. I have pinched the hoses enough to leave about 30 degrees of needle flutter, any less and the reading falls to zero
    3. With that established, I have connected the gauges normally for synchronisation
    4. I keep the idle at 1750 rpm as per the manual
    5. Nothing was too far off, cylinder #3 was pulling a bit more vacuum than the others

    So here's where the problems start: When I go to adjust say, the 3/4 balance, turning the screw does not change the dials. I can turn it either way, far enough to hear the engine lope and lose rpm. But the dials barely change. What is going on? I have done this before so I know I'm only after very small changes but I'm not getting anything here. My only theory is that the clear PVC tubing I am using is either leaking or perhaps not crushing properly in the vacuum pinch bolts?
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    Member BusaSteve's Avatar
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    From what I understand there should be three screws. The left hand one is to sync carbs 1 and 2. The right hand one is to sync carbs 3 and 4. The centre one is to sync the two pairs....1 & 2 and 3 & 4 to the same setting. Although others say you set each carb to the fourth one which is the base setting. Also the valve clearances are supposed to be checked first.
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    Member GreenMeanie's Avatar
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    I'd check for a blockage in the vacuum tube on the body of the carbs.
    You can borrow my electronic balancer if you like Tom if you want to check the response against another instrument.
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    Member Duffman's Avatar
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    Never needed to myself, but have been told that putting oil in the hoses will dampen the fluctuations.
    As long as the hoses are forming a 'U' shape the oil won't be sucked in.

    Quote Originally Posted by BusaSteve View Post
    From what I understand there should be three screws. The left hand one is to sync carbs 1 and 2. The right hand one is to sync carbs 3 and 4. The centre one is to sync the two pairs....1 & 2 and 3 & 4 to the same setting. Although others say you set each carb to the fourth one which is the base setting. Also the valve clearances are supposed to be checked first.
    Usually the throttle cable is rigidly connected to #3 butterfly, so everything is done relative to that.
    Adjusting #2 also adjusts #1 , so #2 gets matched to #3 first.
    Last edited by Duffman; 20-05-2017 at 04:44 PM.
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