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carb jet issues,

Discussion in 'XJ Modifications' started by Sal Raciti, Jun 22, 2018.

  1. Sal Raciti

    Sal Raciti New Member

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    my 82 xj650 has pods, straight exhaust, shimmed needles, idle jet from 40 to 43 and mains from 110 up to 120. the bike idles the best it ever has, but when i accelerate the bike seems to bog or sputter,
    i was wondering if the main jet is too big at 120. it still seems a little lean tho? i did nothing but shim the needles up, i did not make them thinner. i also tryed taping the pods off just to see if it was getting too much air, it ran worse. Any suggestions? other than putting the airbox and cones back on.!
     
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  2. Sal Raciti

    Sal Raciti New Member

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    the air box is long gone, ive chopped the tail and seat so no room for box anymore, boo hoo
     
  3. chacal

    chacal Moderator Moderator Supporting Vendor Premium Member

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    #120 main jets for a 650 is way too large, and shimming the needles just makes the situation worse. #43 might be one size too large for the pilots, but you can probably get by with them if you crank the mixture screws in a bit........although I would recommend the use of a Colortune plug to adjust the mixture screws, rather than guessing. And of course re-synch the engine, and check/adjust the valve clearances if you have not already done so.
     
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  4. k-moe

    k-moe Pie, Bacon, Bourbon. Moderator Premium Member

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    +1 your mains and needle shim are causing the bog. Way too rich.
     
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  5. Polock

    Polock Well-Known Member

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    if you think your lean, try this, 4th gear at the rpm you think is lean at about 3/4 throttle. now close the throttle as fast as you can and see if you notice a slight surge forward.
    only lasts a instant and sometimes doesn't do anything.
    if it's lean, you cut the air and the mixture improves for a instant and you can feel it
    but your way rich so start with that
     
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  6. Sal Raciti

    Sal Raciti New Member

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    Thanks Chacal,
    my bike was so lean before, so i might try taking the shims out and putting in a 116-119 main? I'm going to try the 43s. my valve clearance is good too. thanks for the quick reply, this is one of the last things i wanted to do before paint.
     
  7. Minimutly

    Minimutly Well-Known Member

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    Whatever you do, do ONE thing at a time....
     
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  8. Sal Raciti

    Sal Raciti New Member

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    Now I took the shims out and it stopped bogging on acceleration, but now it won't idle. Just got new intake boots in the mail, putting those on now.
     
  9. Sal Raciti

    Sal Raciti New Member

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    20180529_141907.jpg 20180708_180608.jpg 20180708_180608.jpg
     

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  10. Sal Raciti

    Sal Raciti New Member

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    New Boots are so snug, Having a bitch of a time getting my carbs back on. I cut out the shape of the seat and I gotta fab that so I stop sliding back, im really gonna have racing stripes in my shorts from the tire!
     
  11. Sal Raciti

    Sal Raciti New Member

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    does anyone know the size of the holes for a #118 and #42 jets? cant find a chart with the 118,
     
  12. chacal

    chacal Moderator Moderator Supporting Vendor Premium Member

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    1.18mm and 0.42mm diameter............
     
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  13. k-moe

    k-moe Pie, Bacon, Bourbon. Moderator Premium Member

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    You'll find that the same thing works for valve shims. The nomenclature is just a rework of the measurement in mm.
     
  14. Polock

    Polock Well-Known Member

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    are you going to ream your own jets?
     
  15. Sal Raciti

    Sal Raciti New Member

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    So I had my stock jets of 110 and 40 just sitting here and 120 /43 seemed too rich, so I was thinking about reaming the 110 to 118 and the 40 to 42 just to try it. But last night I got my bike to idle and accelerate great with the 120/43 jets in. Maybe I won't ruin those stock jets just yet.
     
  16. Sal Raciti

    Sal Raciti New Member

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    I can also only find a drill bit for 1.15 mm
     
  17. k-moe

    k-moe Pie, Bacon, Bourbon. Moderator Premium Member

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    You need to know where to look.

    I can't seem to link it without getting a redirect to their web provider, but Grainger carries drills in that size. Most other industrial suppliers will too. McMaster-Carr is another that comes to mind.
     
  18. Polock

    Polock Well-Known Member

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    a reamer is what to use, you could try one of these
    https://www.mcmaster.com/#reamers/=1dser0s
    but just buy new jets
    Reamer
    Dia. Flute Overall Number
    of Flutes Cutting Dia.
    Tolerance For Use On Each
    Straight Flute

    0.0460" 1/2" 2 1/2" 4 0" to 0.0002" Aluminum, Brass, Bronze, Iron, Plastic, Stainless Steel, Steel 8803A109 $18.93
     
  19. k-moe

    k-moe Pie, Bacon, Bourbon. Moderator Premium Member

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    For jets it really doesn't matter if you use a reamer or a drill. The work is being done by hand, so the drill bit isn't going to waller out the hole like a power-driven bit will.
    If we were making a hole that required something to fit snugly inside of it, or were making new jets for sale I'd agree (drill undersize then ream).
     
  20. Polock

    Polock Well-Known Member

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    true, your going to ruin it either way :)
    drills are made under size because the holes they make are bigger than the drill, not so with reamers
     
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