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bogging down at 3500+ RPM

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    bogging down at 3500+ RPM

    My '81 GS450 L is bogging down a lot at all RPMs past 3500, but mainly between 3500 and 4000. It worked fine before and heres what changed: completely tore bike apart (to restore/paint) and reassembled it. I didnt mess with the engine cuz it worked perfectly before my project. I did open up and clean the carbs, replaced stock air filter (with K&N), added a small breather filter for the valve cover (since I ditched the air box) and replaced the valve cover gasket. I'm thinking its either the jets or timing. Any suggestions on how i should solve this?

    #2
    I had the same problem, and it was diagnosed here as retarded advance timing.

    Re-do the timing. Set it at idle, then set the advance timing at 2500rpm. Take her for a test spin and tell me what happens.

    Of course, my Tach promptly broke, so testing that theory has to wait until I can afford to replace the cable. :?

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      #3
      Did you say you replaced the stock air filter with a K&N, if so did you rejet? you did say you ditched the airbox so you have a large increase in airflow,and are therefore running way too lean, try pulling the choke on next time it does it and seeif that makes any difference , if it does you need bigger main jets.
      Dink

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        #4
        consensus: Jets

        All the riders I've discussed this prob with have agreed that it is a problem with my jets. Next step... replacing them. Any suggestions on what kit to go with or what GS model to rip jets off of?

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          #5
          If you can get a kit from Dynojet or K&N that is the best thing to do. You get adjustable needles and usually two or three of sets of mains. Otherwise you have to take a hit or miss approach.

          You can try checking the position of the washer on the needle that is on the slide. If there is a washer over the e-clip try putting the washer under the clip to richen it up. If there aren't any washers go to Radio Shack and get some for electronic use. They should have some small enough for your needs. Again, put them under the clip. Also go up a size or two on the mains.

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