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gs700 6k(ish) stumble

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    gs700 6k(ish) stumble

    I've been tuning up a gs700 for a friend and just need a little help before I order parts. The bike is a stock gs700. Stock exhaust, stock air box with oem style foam uni air filter, stock carbs and jets. I've done the following work on it.

    Adjusted valves
    New plugs
    Thoroughly cleaned carbs
    New o-rings in carbs
    New intake boot o-rings
    Vacuum synced the carbs
    Adjusted pilot screws with highest idle method (had to go about a round further out than originally set.)
    Carb boots are in great condition, no leaks

    The bike now starts better than ever, it idles smoothly around 1100rpm, idle doesn't hang, revs smoothly off idle, and runs up to 10k sitting in the driveway in neutral. The problem is when under load, especially in 4th and 5th gear, the bike doesn't want to rev above around 6k. It seams like it just hits a brick wall. I can hear it slightly surging but not sputtering or popping. It just doesn't want to rev any higher. occasionally i can coax it a little higher by backing off the throttle a little and then going to WOT again.

    My initial thoughts at that the mains are too small, causing a lean condition. What gets me though is that everything is stock, and i figured that the oem jetting "should" be right, although I've heard that these 700's were notoriously lean from the factory.

    I'm just looking for any other ideas, or for someone to confirm my thinking before I order larger mains. And if this is the case, should I go 1 size or 2?

    #2
    Probably do need to go up one or two sizes on the main with the Unifilter. 6k is about where it comes off the needle and onto the main. 6-7k is usually about where the 700s really pull hard. Is the snorkel still on top of the airbox?

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      #3
      Yes, the snorkel is still on the box lid.
      I was wondering if that filter did flow a bit better than stock, therefore necessitating larger mains. I think I'll order 1 and 2 size larger mains and do some plug chops.

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        #4
        Hi,

        If it's not the jetting, then move on to the other usual suspects; petcock, vacuum line (leaking or collapsing?), or even the cam timing. Anyway, just my profound glimpse into the obvious.


        Thank you for your indulgence,

        BassCliff

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          #5
          Forgot to add to my maintenance list...

          New OEM petcock
          Clean fresh fuel

          I doubt cam timing is an issue, as it runs up just fine under no load. But its always good to have other options to look at!

          BTW, does anyone know what type of mains these BS32ss carbs use? I don't remember off hand and would like to order without pulling a bowl. If I remember right its the 100.604 (large round head) mains, but again, I just dont remember for sure.

          Comment


            #6
            Originally posted by atvpyrofreak View Post
            Forgot to add to my maintenance list...

            New OEM petcock
            Clean fresh fuel

            I doubt cam timing is an issue, as it runs up just fine under no load. But its always good to have other options to look at!

            BTW, does anyone know what type of mains these BS32ss carbs use? I don't remember off hand and would like to order without pulling a bowl. If I remember right its the 100.604 (large round head) mains, but again, I just dont remember for sure.
            It is the larger round mains. Stock main is a 122.5.

            Comment


              #7
              I've seen bad ignitors do this.
              1983 GS 1100E w/ 1230 kit, .340 lift Web Cams, Ape heavy duty valve springs, 83 1100 head with 1.5mm oversized SS intake valves, 1150 crank, Vance and Hines 1150 SuperHub, Star Racing high volume oil pump gears, 36mm carebs Dynojet stage 3 jet kit, Posplayr's SSPB, Progressive rear shocks and fork springs, Dyna 2000, Dynatek green coils and Vance & Hines 4-1 exhaust.
              1985 GS1150ES stock with 85 Red E bodywork.

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