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Jetting questions (not a GS, but close)

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    #31
    Update:
    Moved needle clips to #2 from top (was on #3). Good news is middle/end is improved, and I can fairly easily avoid the sloppy area by keeping throttle under 3/4 between 4.75k and 6.25k (ideally a smooth roll-on, but that's the touchy area). I hypothesize position #1 would pretty much eliminate the soggy area, but reduce performance at all other revs.

    Bad news is the flat spot off-idle is back, as I thought it would be. Not quite as bad as last time I tried position #2, probably due to the float adjustment, but it's quite annoying. Best off-idle performance was actually position #4. At #1 I'm sure you could barely get the bike moving from a stop.

    Overall, I think position #3 is better, since I can actually get a good launch, and if I'm very careful to do smooth calculated roll-ons, power at all revs is a little better.

    I could try #2.5 with a spacer, but I know what'll happen. Mid/top will have slightly more blubbery potential and low end will be a little better.

    So my needles/slides come in too lean and go out too rich too soon. Or, stated the other way, I need the needle circuit to come in richer and go out leaner and/or later. Can't go too much later, redline is only 8.5k.

    Possible fixes:
    1) Different needle jets? No experience here -- do they enrichen more at a certain range or would this affect the entire needle circuit evenly? If it's even, this'd do me no good -- I've got to bias the needle circuit toward leaner at the end.

    2) Different needle taper or longer needles? I'm pretty much lost here as well. Those Mikuni needle codes are confusing.

    3) Retard slide action. Epoxy holes and drill to smaller size. I'm thinking even smaller than stock. This is the one I could try today without spending additional $$$. However, I'm not sure it would do more than mask the problem, and probably only in the lower gears. During a long run in 3rd or 4th or 5th the slide will have plenty of time to rise, regardless of the size of that orifice, right? So that'd end up being another balancing act between throttle response in the lower gears and keeping the slide SLOW enough to not get over-rich in the higher gears. The size of the slide hole is for more of a damping effect, right?

    4) Stiffer slide spring? I just now thought of this one. Rather than change damping, this would actually change how MUCH vacuum is needed to get the slide to a particular position, right? So it would delay full slide opening to bigger throttle openings/higher revs?

    Very eager to hear everyone's take on these thoughts!
    Last edited by Guest; 11-24-2007, 04:51 PM.

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      #32
      Now that I think about it, I think I will have to try making the slide holes smaller. I remember when I drilled them the midrange thing got noticeably worse, but I just dismissed that as aggravating whatever else was the REAL problem...

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        #33
        Slide holes filled with JB Weld and drilled to about 1.5mm (I think stock was about 2mm), which is about half what they were (3mm). That should give me a good feel for the effect. Just waiting for some time to re-install and a break in the weather to test...

        Note regular epoxy (at least the stuff I tried) is not very "drillable". Just kinda melted and yielded a very crappy hole. JB Weld (second try) drilled cleanly, so there is a difference.

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          #34
          Got the carbs back in the bike. I also stretched out the slide return springs a bit, which increased the free length somewhat. I'm not sure if that'll make any permanent difference, but I've heard it can be helpful.

          Anyway, I took it out for a test ride and dumped it. Was too wet to get a good feel for the changes, but the good samaritan who drove it home for me (clutchless) said it ran great. ;-) (see thread in off-topic)

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