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Need Some help. Running rich

Discussion in 'The Garage' started by avmagneticz, May 26, 2016.

  1. avmagneticz

    avmagneticz XS650 Member

    Hi everyone, so I'm trying to get my bike running right. Here's what I got. And here are my issues
    73' bs38 carbs. One up pilot, two up main jet. Mix screw 1 turn out. Carbs never been synced. Carbs are original rebuilt awhile back. Good shape.
    80' engine, uni pod filters, open short headers, 1mm overbore. New build less then 1000km
    So I've been running the bike with stock carb settings and noticed it was lean up top. Idle was a Lil lean as well and had the mix screw about 2.5 turns out lol. But left plug was always rich.

    Switched to my current jet setup. Idle has changed drastically. Bike runs better up top I feel I can almost go further in 5th gear now. But when I really give on the throttle it stutters. As if something up in the midrange. 4-5 gear not so bad.
    Anyways the bike got worse I notice a tiny bit of black smoke on left side. I pulled plugs both pretty black. Cleaned em up rode a few times pulled em left super black, and right side looks so so. Just pulled the carbs checked float height. Looks OK at 25mm. Checked fuel filter. Clean. Put new plugs. Fired it up right side shot a red flame or two and left a Lil black smoke again. How is it so rich at idle. What things should I check. I know this must be a carb issue. Timing is good bike sounds great when it's working properly. Starts so easily.

    I'm new to this so I'm running out of ideas I don't wanna fuck anything up. I almost wanna just throw money towards new round slide carbs. What else should I check. Why is the left always more rich. I never looked at the diaphragms... I dunno what else. The bike was running I sprayed carb cleaner everywhere found no leaks.

    I'm kind of all over the place as you can tell. Any suggestions would be helpful thank you.
     
  2. TwoManyXS1Bs

    TwoManyXS1Bs BBQ Hunter Top Contributor

    Do your carbs have the single enrichner on the left carb, blocked off on the right?
    If so, that may be something to check.
    Research that enrichment system, note that it draws air from under the left diaphragm.

    I have the earlier dual enrichners, and had to rebuild them. Have a look at my album pics, starting with this one, and hit 'previous' for another six.

    [​IMG]
     
  3. avmagneticz

    avmagneticz XS650 Member

    Yes my carbs have the one choke on the left. I didn't even think of that. Recently I haven't even been using it cause the bike dies right away with it on. And I'm talking cold starts only. I usually start my bike and give it a tiny throttle till warm. Anyways. You think this could be causing an issue. I reviewed your photos. So you cleaned the seat and replaced the rubber. But if mine was leaking would it not cause a lean mix on the left? I'll have to look into this as well
     
  4. TwoManyXS1Bs

    TwoManyXS1Bs BBQ Hunter Top Contributor

    Well, it's a crapshoot, my best guess with those clues.
    '73 carbs with single enrichner on left, your leftside carb issue.

    Expect the unexpected. Let us know whutcha find...
     
  5. 5twins

    5twins XS650 Guru Top Contributor

    18,849
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    You've made no mention of your needles or what clip slot they're set in. Many times, when you increase main and pilot sizes, you have to lean the needle setting. The three circuits in your carb bleed over or overlap into the ones next to them. Changing one can effect the circuit next to it. You now have larger pilots adding richness to the lower midrange and larger mains adding it to the upper midrange.

    [​IMG]
     
  6. avmagneticz

    avmagneticz XS650 Member

    It's the one setting I haven't checked yet. I'm assuming they are on the stock setting which is I believe the third notch. So you suggest I try that. I just wasnt sure if it was stuttering cause the mid was to lean. Must be to rich.

    Tonight I'll remove them and lean it one notch. Would that affect the idle as well? Since the overlap
     
  7. 5twins

    5twins XS650 Guru Top Contributor

    18,849
    9,657
    688
    Stuttering or stumbling through the midrange under heavy throttle applications is a classic sign of what can happen if you install larger mains but don't lean the needle setting.

    You said the carbs were rebuilt a while back. If aftermarket rebuild kits were used, they may have contained a replacement generic needle. Sometimes those are incorrect for the year of the carb and don't work very well. Check the needle number you have. Stock should be a 4JN19 and stock clip position was 4th slot from the top. The rebuild kit generic needles I've run across are either a Y22 or a Y31. The Y22 is a match in length to your original but the taper may not be the same. It's best to stick with the original needles.

    Yes, leaning the needle will effect the upper portion of the idle circuit. Sometimes it will create an off-idle flat spot or lean stutter and that calls for a size larger pilot jet. But, you already did that. Hopefully, changing the needle setting is just going to make your main and pilot jet size changes work correctly.
     
  8. avmagneticz

    avmagneticz XS650 Member

    Thanks I appreciate it I believe your right. Keep you guys posted.
     
  9. avmagneticz

    avmagneticz XS650 Member

    Ok leaned out the clip it was on stock location also the needle was Y22 anyways bike isn't stuttering and seems to be running pretty well! I just need to make sure my fuel mix screw setting is correct
     
  10. avmagneticz

    avmagneticz XS650 Member

    For some reason tonight ir was sputtering down low in the Rpms. When I would go to take off in first ir would do it a lot and backfire a bunch. Then eventually go. I wonder if it's cause I used different fuel today. 87 where as before I had 94 premium stuff. I tried to see the flame I think it was mostly blue comin from the left side now. Wonder if I need to up the mixture screw
     
  11. avmagneticz

    avmagneticz XS650 Member

    Left side continuously fouling plugs and doesn't seem to react when adjusting mix screw. Also left side is the one with the plunger for choke. I dunno its unpredictable now it'll run good for a minute then act all fucky
     
  12. Sounds like the first minute is before the plug fouls and then you are running on an intermittently firing left cylinder? I had the same problem and it turned out to be a failing brass float in the '73 carbs.

    Could definitely also be something to do with the choke mechanism, but that's beyond my knowledge sorry.
     
  13. avmagneticz

    avmagneticz XS650 Member

    Interesting what causes the float to fail a hole or crack over time? Definitely worth a check. The right side is great right now
     
  14. Mine was a broken float post (pretty common issue from people dropping the Carb while working on them) that I just couldn't repair no matter how hard I tried.

    Ended up replacing the Carb out of desperation.
     

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