'86 500 Slow Speed Jet

Discussion in '1st & 2nd Generation 1983-1989' started by Guaire, Jan 15, 2018.

  1. Guaire

    Guaire New Member

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    I got this 500 to run well after solving my petcock problem. But, it still had a tendency to run weakly at idle until it warmed up. I had to be careful about keeping it choked until it would hold idle. Acceleration off idle seemed a little weak until the throttle opening made it past 1/4 open. Then it feels great.
    Assuming my jets are stock, an non CA model, I should have a 38 slow speed jet. 99103-MV9-0380. Would going up to the same jet, but 40 size, fix the low performance off idle and weak idle cold?
    Cheers,
    Bill
     
  2. Captain 80s

    Captain 80s Member

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    Provided everything else is clean and properly adjusted, yes, it will fix it. I do it to every one of my 500s. But it does sound like you have some partially dirty pilot jets. It shouldn't be that bad.
    You can also clean it up by defeating the limiting caps on the pilot screws so you can back them out a little more to allow more fuel as well. But if I had my carbs out and had the jets, I would personally swap them.

    Again, this is all assuming you have clean, properly adjusted carbs. Which is rare.
     
  3. Guaire

    Guaire New Member

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    Thanks, Captain 80s. After I bought this bike last year, I overhauled the petcock, fuel lines and I replaced the needles. While I had the carbs off, I blew them out and sprayed them with cleaner. I didn't do the whole disassembly and dipping. What I did paid off. Performance in the right throttle range got nice and snappy.
    I still have the tupperware off, the tank, seat etc. while I replaced the old rubber brake lines with steel braided. When the temp gets up a bit, I will also rebuild the rear master cylinder.
    Time to pull the trigger on 4 slow speed jets!
     
  4. Captain 80s

    Captain 80s Member

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    When you have the float bowls off, switch their positions so the little tabs are on the opposite side of the pilot screws, so they can be adjusted anytime. You'll see what I mean.
    Also, if you haven't already replaced the float bowl o-rings, get some Viton -041 orings for the float bowl gaskets. They are dirt cheap and the perfect fit.
     
  5. jeremyr62

    jeremyr62 New Member

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    Can't disagree about the reason but I went to 42 slow jets. I knew the 38s were too small because if I gave it a fistful it would stumble and not rev out cleanly. With the 40s it was much improved but with 42s it was perfect. YMMV.
     
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  6. Guaire

    Guaire New Member

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    AHA! Timely suggestion.
    When I opened the carbs I assembled them with new gaskets. The originals were definitely shady.
     
  7. squirrelman

    squirrelman Member

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    neither chemical cleaners nor compressed air are sufficient to clean a slow jet properly. in addition to those, a .010" steel wire should be pushed through to remove deposits and check that the hole is fully open.
     
  8. Guaire

    Guaire New Member

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    I've got four fresh 42s on order.
     
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