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    #1

    wont rev above 4500

    So running kn filter aftermaket exhaust 115 mains stock pilots and screws are all standard setting... did carb balance, valves are good and needles are raised 1 ring.

    No rev above 4500... just bogs. Rides great otherwise... just wishing I could use the entire rev-range.

    Petcock is fine and fresh gas. It revved in the garage OK with 102. I changed to 115 thinking the hesitance to rev up high was in regard to being lean. Am I too rich?

    The pilot air screws dont do a thing to the idle unless theyre screwed all the way in... so I left them at 1.25 turns.
    Last edited by Guest; 05-20-2012, 01:45 AM.
    Tags: None
    #2
    Hi,

    What does a plug chop tell you at WOT?



    Thank you for your indulgence,

    BassCliff

    Comment

      #3
      Doing that in the am...

      New development... its not the timing advance, everything moves freely. Also, got it up to 60 down hil... dropped it into second and let the motor engine break up to 7K rpm. Now the bike will rev straight up to 6K no issue. Its having a crap time on cold starts though. Really hard to get it cranked after cooling down about an hour or two.

      Comment

        #4
        Also took the plugs out from today... theyre a rusty brown.

        Comment

          #5
          If it ran better on 102.5, make a smaller change to see what happens... Maybe 107.5? Wait, are you sure it was even too lean with the 102.5?


          Life is too short to ride an L.

          Comment

            #6
            Well, with the aftermarket pipe and filter... I thought so.

            But the bike had these same 'symptoms' where, in the workshop, it didn't want to rev very high, but I was accounting that to the 102.5 jets.

            I'm going to do a compression test. I'm starting to get a sinking feeling I may need rings.

            I have a set of 112's that I can try.

            I tried unscrewing the Fuel screws to 1 full turn, and that didn't help much at all, it's almost like the bike is just running on the pilot circuit. Float levels are set to 26mm... and the carbs have been thoroughly boiled and everytime I take them off, I go through every jet/passage and hole and clean it.

            I'm just at a bit of a loss...

            I'm going to try the following tomorrow:

            - Compression test.
            - Install my second set of slides with thinner needles and spring/plastic washers
            - Install 112 jets.
            - Double-check petcock screens.
            - New plugs
            - Re-set the fuel and air-screws.
            - Re-check carb balance.

            If that doesn't work... I'm at a loss... is it normal for the Air screws to have NO affect on idle unless fully closed? There was no idle change when I performed a check on this earlier... but judging by how crappy it's running, it may just be masked by a larger issue.

            Comment

              #7
              do the jets first.

              Comment

                #8
                Read the symptoms part on page 18.....

                http://www.vintagesnow.com/Carburetors_files/vmmanual.pdf
                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

                  #9
                  Originally posted by Dreef1999 View Post
                  do the jets first.
                  I just read this: http://www.iwt.com.au/mikunicarb.htm

                  So it's obviously my needle/main that are the issue. The bike only runs up to 1/4 throttle, hence why it bogs after 4500 rpm, because it IS just running on the pilot circuit.

                  So, I'm going to swap jets first.

                  Originally posted by chuck hahn View Post
                  Read the symptoms part on page 18.....

                  http://www.vintagesnow.com/Carbureto...s/vmmanual.pdf
                  By that logic, it's running too lean.... however, my above quote about the pilot circuit makes that hard to determine at the moment.

                  Comment

                    #10
                    Im not diagnosing anything..just happened to see this and passing on whatever may or may not be of value..yours to read and use if you can..
                    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

                      #11
                      I had the wrong needles... and the stock jetting is supposed to be 100. Throwing in the 102.5's and the correct needles.

                      God I hope this fixes it.

                      Also... lots of sediment in the bottom of the tank.... God damn it. More vinegar to the rescue.

                      Comment

                        #12
                        Looks like I have a set of 750 and 850 carbs... same bodies, different jetting and needles.

                        What fun.

                        Comment

                          #13
                          Once again, here we go, someone asking for help and then ignoring good advice from those who dispense it.
                          Check Cliffs post, post #2 have you done a pug chop, as suggested.???????
                          Last edited by Guest; 05-20-2012, 05:38 PM.

                          Comment

                            #14
                            Yes... twas not ignored. All plugs were brown @ wot this morning...

                            just fiddled with the needles and the only thing that works well... not perfect.. is 102.5 jets with 5DL36 needles on the highest notch. Meaning sitting waaay low in the jet. I may try going to the 5F21 needles on the middle setting and see what that does. I was running them on the second clip from the bottom with the 115's and was experiencing the issues not revving over 1/4 throttle.

                            Comment

                              #15
                              Oh and did a second chop with new plugs after installing the 36 needles on the middle clip and they were soot black.

                              Comment

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