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Bullet 500 Mixture Adjustment?

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  • #1

    Bullet 500 Mixture Adjustment?

    I need help adjusting the mixture screw for my RE Bullet 500.
    Recently the petrol has been burning really rich, resulting in the spark plug going black very quickly. So I have been trying to adjust the screw.

    One of my problems is that the screw doesn't turn properly anymore. It used to be able to screw out by a few more turns, now it only turns a few times and then it gets very difficult to turn. I'll have this checked out by a mechanic next time I go in to Mathura. (To replace my front wheel bearings which are stuffed and are slowing the bike down dramatically).

    My next problem is getting the mixture perfect. I have adjusted the screw and taken the bike for a ride quite a few times, but so far the best I have been able to get the mixture results in the spark plug getting slightly stained but basically remains clean, but the very top of the spark plug turns blue.

    I don't want to unscrew it any further because even though it's not burning lean enough yet, I don't know what the blue means. If I screw it in anymore then it starts burning richer again, so I don't think the blue on the top of the spark plug can be from the mixture being too lean. I also don't want to continue riding the bike until I know how to proceed.

    What does it mean when the very top of the spark plug goes blue?

    Thanks
    Tags: None
  • #2
    Query Approved.
    :)

    Comment

    • #3
      Today I realised that I could be turning the screw the wrong way. Maybe it would make it leaner if I screwed it in more. I tested it out but that didn't work.

      The manual says to turn it 3 half turns out.

      Today I tested it at 2 half turns out and it was pretty black, at 1 half turn out it was really black, so I think that screwing it in must make it richer.

      Therefor I'm really not sure what to do. If screwing it in makes it richer and screwing it out as much as I can gives it a brown/black stained look with a blue top, how can I do it?

      One thing to consider is that my Bullet has a larger jet in there at the moment. So it is putting more fuel in than the standard jet does. This means that the mixture screw will have to be a bit different to another standard Bullet 500.

      Do you think that there is some special spot in between the black (burning rich) point and the stained (spark plug tip turning blue) point that is perfect? I can't see how there would be a point in between these two that would allow the spark plug to burn cleanly, also when I adjusted the screw to the richer mixture, the bike had alot more power.

      I really don't know what to do, if someone can guide me in the right direction then I can test ride it and slowly get the adjustment perfect. But right now I'm not totally sure whether I am screwing it in the right direction and whether the screw is stuffed and is now limiting my ability to adjust the mixture towards the leaner side.

      Can someone please help me out?

      Thanks

      Comment

      • #4
        hey, first see the hand sketch, sorry for poor drawing.



        2) Now if it is on the Air box side then its AIR screw and you can only adjust the air through this screw. In that case clockwise turn will make the mixture richer and anticlockwise will make it lean.



        ENJOY.
        sigpic

        Comment

        • #5
          I didn't really follow that picture. There are two screws on the carby. One is the idle (pilot jet) and the other is the mixture

          According the Pete Snidal's Bullet Manual:

          The Pilot Jet
          The pilot jet affects idle mixture. Setting your pilot jet involves getting the machine warm, and then adjusting the idle
          stop screw for slowest possible "clean" tick-over, or idle speed. First, be sure your throttle cable has at least I /8-3mm
          slack at full closed. Before starting the engine, ensure that shutting the throttle full off from 1 /2 or so results in an
          audible "clack" as the slide hits the stop. If not, look to your cable routing and condition. Then, adjust the pilot jet
          screw for fastest engine speed. Then reduce the speed with the stop screw once again, and repeat the pilot jet
          adjustment. Do these until you get the best possible idle adjustment. Sudden increases of throttle should not cause
          the engine to "go flat" or die. The pilot jet is an "air bleed" - tightening it makes for richness, loosening leans it out.
          As far as I can tell, tightening it does indeed make it richer. At least in my case.
          I tried that method today, but I wasn't that successful. It is running alright but is still not perfect. I'll probably get the mechanic to fix it up when I go there.

          Comment

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