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Flat spot coming off idle.

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    Flat spot coming off idle.

    I've put about 300 miles on the '79 GS1000E I rescued, and everything seems to be well. My only problem is a flat spot after idling for a minute, like maybe the length of a red light. If I don't blip the throttle before pulling away, I get a pretty bad flat spot, just as I roll on the throttle and release the clutch. Haven't decided if it's getting too much fuel or not enough. The bike starts easily, even in the dead of winter. Pull the choke knob and hit the starter and it's running, every time. Runs great all the way up to redline. Will idle at 1000 rpm all day long. Doesn't pop or backfire. K&N filter in the stock airbox. Stock exhaust that the PO drilled out the ends of. New intake o-rings and carb o-rings after a thorough carb cleaning. All the jets and needles are stock. Float levels were checked. Haven't synced yet. Any ideas? Haven't really dug into it yet. Probably a simple fix or adjustment. Just doing a little brainstorming. I plan on posting this in my thread in the Project/Rebuild section also, so no busting my chops for double posting, eh? Thanks!

    #2
    Stock VMs or other carbs? If VMs, then set the pilot ( bottom ) screw at around 7/8 to 1 turn out from bottom and the mixture ( side ) screws at 2 turns out. Thats the basic setup that i have gotten from asking similar questions. What position is the clip on the needles..center groove is factory setting. Also be sure the thinner washer is below the clip and the fatter one is on top.
    MY BIKES..1977 GS 750 B, 1978 GS 1000 C (X2)
    1978 GS 1000 E, 1979 GS 1000 S, 1973 Yamaha TX 750, 1977 Kawasaki KZ 650B1, 1975 Honda GL1000 Goldwing, 1983 CB 650SC Nighthawk, 1972 Honda CB 350K4, 74 Honda CB550

    NEVER SNEAK UP ON A SLEEPING DOG..NOT EVEN YOUR OWN.


    I would rather trust my bike to a "QUACK" that KNOWS how to fix it rather than a book worm that THINKS HE KNOWS how to fix it.

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      #3
      Sync your carbs and see if it goes away
      1978 GS 1000 (since new)
      1979 GS 1000 (The Fridge, superbike replica project)
      1978 GS 1000 (parts)
      1981 GS 850 (anyone want a project?)
      1981 GPZ 550 (backroad screamer)
      1970 450 Mk IIID (THUMP!)
      2007 DRz 400S
      1999 ATK 490ES
      1994 DR 350SES

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        #4
        Stock VM carbs. I can't swear to the needle position right now. It's been 6 months since I did the carbs, but I can swear that they are all the same and that they are all in the position I considered factory at the time I did them. Is it possible that they only have 1 groove? I seem to remember that and remember thinking that it was odd. I was very meticulous about making sure they were all the same and all correct. I really need to do the syncing. Gonna shop for a sync guage now.

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          #5
          Originally posted by FLHGSRay View Post
          Gonna shop for a sync guage now.
          Morgan carbtune, done, done...

          Carbtune motorcycle carburetor synchronizers;polycarbonate tool pouchs;for motorcyclists
          '85 GS550L - SOLD
          '85 GS550E - SOLD
          '82 GS650GL - SOLD
          '81 GS750L - SOLD
          '82 GS850GL - trusty steed
          '80 GS1100L - son's project bike
          '82 GS1100G - SOLD
          '81 GS1100E - Big Red (daily rider)

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            #6
            Originally posted by hikermikem View Post
            Morgan carbtune, done, done...

            http://www.carbtune.com/

            mine did the same thing before and after the carb rebuild, i got the vac sync gauges from Z1 for like 50 bux, sync'd em and was done done, runs so super sweet now n sounds better too.we can actualy talk to eachother up to like 45 mph without screaming even with pods n a 4 into 1.hehe
            sync n be done yup

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              #7
              Does it also bog when accellerating from low rpm say 2000 - 3000? If so open your air screws half a turn if that helps you know its rich and can fine tune from there.
              Otherwise floats valves may be leaking and loading up the carbs.
              1979 GS750E

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                #8
                I bought a motionpro carb sync. Wish I had bought the Morgan

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