Carb Sync Help

Discussion in '1st & 2nd Generation 1983-1989' started by Calflash, Oct 7, 2009.

  1. Calflash

    Calflash New Member

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    I've looked at the pic's and I'm still not sure where to hook up the lines to sync the carbs. Are the ports the ones with the "rubber" tubes that look like caps? All the ones I've ever done have screws in the ports.:crazy::crazy::crazy:
     
  2. tinkerinWstuff

    tinkerinWstuff Administrator Staff Member

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    my bike has screws in some of the ports that aren't being used. They are right below the rubber boots that connect the carbs to the cylinder head. Two of the ports have vaccuum ports screwed into them; one is connected to california emissions crap, and the other was for (a now nonexistant) vacuum shutoff for the fuel tank. Someone may have screwed in vacuum ports into yours for balancing and then put rubber boots to cap them off?
     
  3. slowbird

    slowbird Member

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    I was told that for a 100% perfect and proper synch the carbs must come out.

    I was also told by another person that a carb synch with the carbs in the bike and it won't be accurate.

    I've had my carbs "Synch'd" twice with my carbs in the bike and there's been no difference.
     
  4. tinkerinWstuff

    tinkerinWstuff Administrator Staff Member

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    I'm thinking you might have that backwards??:confused:

    You can do a bench sync with the carbs out to get them "close" but the engine must be running with vacuum guages on each cylinder to dial it in perfectly. What you are doing is matching each of the carb butterfly valves by measuring vacuum behind them. If one butterfly is just a miniscule amount different from another, there will be a difference in vacuum behind it.
     
  5. NorcalBoy

    NorcalBoy Member

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    ding, ding, ding....we have a winner :smile:
     
  6. slowbird

    slowbird Member

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    What I posted may be incorrect...but that is what I was told.

    I have yet to find anyone to properly synch my carbs.

    This spring hopefully.
     
  7. tinkerinWstuff

    tinkerinWstuff Administrator Staff Member

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    Sorry to take this further away from the OP, but since it's still related to balancing, I'll say this:

    Since you've attempted balancing and don't sound happy with it, I'll suggest you check a few other things. Balancing is real easy and the butterflies are either matched or not. It's all there on the guage and it's just that simple.

    But, because the butterflies are matched, it doesn't mean the motor is running balanced. In theory - you could have a cylinder that's not even running and still "balance the carbs"

    However, there are other factors that go into getting the engine to run balanced. The first would be having the valve gap matched and even along with the condition of the cam lobes. Second would be float levels in the carbs being set properly. Third could be a partially blocked jet and 4th could be the needle/seat screen. There are probably other things that could be added to the list. My point is that the "balancing" of the carb with the gauge is the last of all.
     
  8. JamieDaugherty

    JamieDaugherty New Member

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    Yes, as mentioned proper carb synch must be done with the carbs on the engine. You need to sych them every time they are removed. A bench synch is enough to just (barely sometimes) get the engine running until you can do a full synch.

    The sych ports should be plugged with phillips head screws. Depending on the model one of the intakes will have a vacuum line going to the petcock. I have a line with a T fitting so that I can capture the vacuum signal and operate the petcock at the same time.

    Good luck!
     
  9. Calflash

    Calflash New Member

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    I forgot to say it's an 87 700. I'll go back and look some more. Thanks for all the help.
     
  10. captb

    captb New Member

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    Just below the carb boot is a screew that plugs the hole. (see pic)
     

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