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    Stutter at full throttle.

    83 850.

    New to me, came w/ a box of spares which includes a dyno jet kit which looks like it has been installed.

    Intake is stock and the exhaust looks stock but doesn't say suzuki or have other markings lead me think aftermarket.

    Up to ~1/2 throttle she pulls fine all the way to redline.
    Past 3/4 throttle she stutters.

    I did the push the kill switch at throttle and look see the plug thingie and they were a nice tan.

    I am thinking carb and not electrical since she will pull full rpms at part throttle but I have no idea if there is an advance issue w/ the timing.

    I am currently running on my first full tank of gas. I have seafoam and lotsa prayers that I don't have to remove the carbs.


    OH mighty gs gurus....where my problem lay?

    Don

    #2
    Your problem lies in one circuit of the carbs...the Primary.

    Either the jets are too small (you never know wht PO's have done to these bike) or the primay circuits themselves are plugged. A good carb clean (soak for 24hrs) and some new orings from cycleorings.com will have you flying happy.

    Welcome to the GSR...

    Comment


      #3
      Originally posted by andmoon View Post

      Past 3/4 throttle she stutters.

      I did the push the kill switch at throttle and look see the plug thingie and they were a nice tan.

      How long did you run it at full throttle before looking at the plugs?
      http://img.photobucket.com/albums/v5...tatesMap-1.jpg

      Life is too short to ride an L.

      Comment


        #4
        If it surges at WOT then you are lean. You will need to up the main jet.

        I would also check the valve clearance.
        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.

        Comment


          #5
          Originally posted by Dave8338 View Post
          Your problem lies in one circuit of the carbs...the Primary.

          Either the jets are too small (you never know wht PO's have done to these bike) or the primay circuits themselves are plugged. A good carb clean (soak for 24hrs) and some new orings from cycleorings.com will have you flying happy.

          Welcome to the GSR...
          Is the Primary circuit the route the fuel takes going through the main jet?

          Comment


            #6
            Originally posted by tkent02 View Post
            How long did you run it at full throttle before looking at the plugs?
            ~5 seconds then hit the kill button.

            Comment


              #7
              Originally posted by chef1366 View Post
              If it surges at WOT then you are lean. You will need to up the main jet.

              I would also check the valve clearance.
              It is more than surging. It stutters similar to what happens w/ bad plug wires.

              Valves have been adjusted. (These things were designed w/ small clearances!)

              Comment


                #8
                Originally posted by andmoon View Post
                It is more than surging. It stutters similar to what happens w/ bad plug wires.

                Could be way too rich at full throttle. What you might expect if it was a stage three kit and stock intake/exhaust.
                Too lean tends to surge, too rich sometimes pops and sputters.


                Originally posted by andmoon View Post
                ~5 seconds then hit the kill button.
                Not long enough to color the plug.

                Originally posted by andmoon View Post
                Is the Primary circuit the route the fuel takes going through the main jet?
                Not with the throttle open, the primary is in use at low throttle openings, it has no effect at wide open throttle.


                Originally posted by andmoon View Post

                OH mighty gs gurus....where my problem lay?
                Your problem lay with you not wanting to take the time and effort to get into the carbs and get them working correctly.

                It is VERY easy to pull the carbs on that 850, the airbox comes out, carbs slide out, piece of cake.
                Go through it all, dip them, clean every passage, replace all the O rings, adjust the floats. Do the intake boot O rings too, they need it for sure.
                Why not put in the jets it came from the factory with, they should be close to what you need with this intake/exhaust.
                Last edited by tkent02; 09-08-2009, 10:52 AM.
                http://img.photobucket.com/albums/v5...tatesMap-1.jpg

                Life is too short to ride an L.

                Comment


                  #9
                  Originally posted by chef1366 View Post
                  If it surges at WOT then you are lean. You will need to up the main jet.

                  I would also check the valve clearance.
                  A very leaky airbox will do this too. For example, if the airbox boots are so old and shriveled that they fall out.

                  Just sayin'.
                  Dogma
                  --
                  O LORD, be gracious to me; heal me, for I have sinned against you! - David

                  Skeptical scrutiny is the means, in both science and religion, by which deep insights can be winnowed from deep nonsense. - Carl Sagan

                  --
                  '80 GS850 GLT
                  '80 GS1000 GT
                  '01 ZRX1200R

                  How to get a "What's New" feed without the Vortex, and without permanently quitting the Vortex

                  Comment


                    #10
                    So this lazy arse got off my arse and removed the carbs.

                    Carbs had the largest dynojet main jets (I think dynojet #165). The inside was pretty clean so I sprayed carb cleaner thru all the passages and in my eye as well (for good measure). I installed the next size down jet and unwrinkled the one wrinkled diaphram, put the stock needles back in (dynojet's needle look identical) and....the stutter diminished but still there in 1st, 2nd & 3rd gear ~ 6500rpms.

                    Loaded w/ confidence, I removed the carbs a second time, replaced the dynojet #160 mains w/ 155s... all in 45mins.

                    One kid needed his bottom wiped and another was watching forbidden TV so I have to wait until tomorrow to check the results of the 155s.

                    Is the stock 112.5 (or similar low number) in the same scale as dynojets?
                    If so this 155 is still waaay too big. Of course the box w/ jets the bike came w/ only has 3 stock main jets.

                    Thanks for all the advise...especially the one telling me there was no lazy way out.


                    Now....what's causing all the popping on decel? Just suttle popping, no back fires. I have no leaks via the visual and spray wd40 test.


                    Don

                    Comment


                      #11
                      Look on the filter side of the carbs and make sure there is a brass jet inserted on the right side of the outer carb throat.
                      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.

                      Comment


                        #12
                        Originally posted by andmoon View Post
                        Is the stock 112.5 (or similar low number) in the same scale as dynojets?
                        Different scale, but WAY too big anyway.

                        Originally posted by andmoon View Post
                        If so this 155 is still waaay too big. Of course the box w/ jets the bike came w/ only has 3 stock main jets.
                        Buy the 4th


                        Originally posted by andmoon View Post
                        Thanks for all the advise...especially the one telling me there was no lazy way out.
                        My pleasure




                        Originally posted by andmoon View Post
                        Now....what's causing all the popping on decel? Just suttle popping, no back fires. I have no leaks via the visual and spray wd40 test.
                        Fry the big fish first, then the little ones.
                        http://img.photobucket.com/albums/v5...tatesMap-1.jpg

                        Life is too short to ride an L.

                        Comment


                          #13
                          TAKE DEEP BREATHS... If going full throttle scares you so much you stutter then back off it a little bit !!!!!
                          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.

                          Comment


                            #14
                            Likely the intake is too free flowing

                            Before getting involved with motorcycles, we all heard that, with respect to air filters, the more free flowing and less restrictive, the better. That might be true on lawnmowers and cars, but with motorcycles the situation is different. Most motorcycles run poorly if the stock restriction levels are reduced. What happens is that they lean-out at higher RPM's because the vacuum is too low to suck fuel up the main jet. I know it sounds counter-intuitive, but sometimes you have to increase the intake resistance slightly (more oil on the foam, thicker foam), to keep the vacuum needed at RPM's above 4000. My bike will not run worth anything with the air filter off, but it runs perfect once re-installed. I tried using free-flowing pod filters, but the performance was worse than with the stock arrangement.

                            Comment


                              #15
                              Originally posted by chuck hahn View Post
                              TAKE DEEP BREATHS... If going full throttle scares you so much you stutter then back off it a little bit !!!!!
                              I am trying to move towards bikes that are closer to their limits at lower speeds. Stutter is good, the last 'UJM' I had was a ZRX1200...Never mind the stutter, it was change shorts time w/ that one.

                              Comment

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