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    carb sync question

    Hi all

    Why is it that the carb sync levels don't line up after you lower the RPMs back down to idle? Anyone have any tricks for adjusting the sync of the carbs?

    Also what is the recommended torque for the 12 nuts that secure the head and cylinders. I did mine to 27 ft/lbs but I am still seeping oil around the base gasket. What would be too much torque?

    Scott

    #2
    That's a good question, I experience the same thing. My guess is because the butterfly valves are closed fuel mixture and combustion play a bigger part than equally opening carbs.

    I've got another question about sync myself, when cyl 1 and 2 were way out of sync with 3 and 4 the idle speed shot up but when I brought them in sync the idle came back down. Is that typical and why would the rpms go up with a potentially unequally running motor?

    Another off-topic question: why the hell did suzuki in all their wisdom put a whole sh1t load of philips screws on the carbs and bike instead of screws or bolts that won't strip. Also why did they put the throttle and choke cable bracket on the carbs in such a way as to inhibit access to the middle sync screw. Even if no one really knows I just had to rant because those two combinations made for a long painful attempt at carb sync. I'm definitely gonna get rid of those philips, I hate them with a passion--especially on the front master cylinder cover.
    Last edited by Guest; 06-21-2008, 12:06 PM.

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      #3
      You can get perfect synch at tickover if you adjust your fuel screws so that your airscrews are all exactly the same (on VMs). That doesn't mean all screwed out the same number of turns as the there are tiny differences in manufacturing of the carbs / screws, and these show up at very low revs. By mucking around you can get these bikes to tickover very sweetly at 500 rpm.

      Suzuki used Phillips screws 'cos they're cheap and easy to put in on an assembly line. 1st mod to do is, as you suggest, replace the blighters with Allen screws.

      (Probably) when you were out of synch, 1 and 2 were offering a higher lift on the slides than 3 & 4. When you synched you effecttively reduced tickover on them, down to the lower level of the other 2.

      What bike are we talking about for head torques, as they are different?
      79 GS1000S
      79 GS1000S (another one)
      80 GSX750
      80 GS550
      80 CB650 cafe racer
      75 PC50 - the one with OHV and pedals...
      75 TS100 - being ridden (suicidally) by my father

      Comment


        #4
        Originally posted by Killer2600 View Post
        That's a good question, I experience the same thing. My guess is because the butterfly valves are closed fuel mixture and combustion play a bigger part than equally opening carbs.

        I've got another question about sync myself, when cyl 1 and 2 were way out of sync with 3 and 4 the idle speed shot up but when I brought them in sync the idle came back down. Is that typical and why would the rpms go up with a potentially unequally running motor?

        Another off-topic question: why the hell did suzuki in all their wisdom put a whole sh1t load of philips screws on the carbs and bike instead of screws or bolts that won't strip. Also why did they put the throttle and choke cable bracket on the carbs in such a way as to inhibit access to the middle sync screw. Even if no one really knows I just had to rant because those two combinations made for a long painful attempt at carb sync. I'm definitely gonna get rid of those philips, I hate them with a passion--especially on the front master cylinder cover.
        I oft wondered the same thing about the phillips heads. But lo and behold, when i bought my 82 1100G, from the factory it came with cap head bolts. Why didnt they do this on ALL the bikes? The 1100E of Mikey Riddles that Steve and I will be working on has the cap heads too...did they reserve these for their bigger more expensive bikes?

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          #5
          In addition, a good set on the valves first, makes all the difference as well.

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