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Ninja EX500 carbs on an XS650?

Discussion in 'The Garage' started by Highside, Oct 20, 2011.

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  2. Hi Barry here. Help please putting ex kaw carbs on xs 650..Can I remove the fuel T fitting? And in stall 90 degree elbows. So I can still run two fuel line from my xs tank? Thank YOU
     
  3. gggGary

    gggGary Stop that! XS650.com Supporter Top Contributor

    Really no need to run two petcocks. but you could ADD another tee and feed from both. I never use the RH petcock on my 77 tank.
     
    peanut likes this.
  4. peanut

    peanut XS650 enthusiast & inveterate tinkerer XS650.com Supporter Top Contributor

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    I'll be needing to sort out the fuel supply to my Kawa GPZ500 carbs shortly myself.

    . Why were BS38s fitted with individual supplies to each carb and not a single supply for both?
    I have never read a user guide for my 79 special ll with BS38s so I am embarrased to admit I haven't a clue what the proper proceedure is for setting the petcocks for starting and running .
    Do both petcocks have the same reserve ? How should the petcocks be set for starting ,town riding and touring etc .
    So many questions ....so little time :laugh2:
     
  5. Demorgan

    Demorgan XS650 Enthusiast

    did the '79 have vacuum petcocks? the GPZ500 carbs DO have vacuum take-offs for this but my 77 has non vacuum petcocks so i removed the barbs from carbs and filled in with "liquid metal". These carbs use 34mm manifolds, which all seem to have vacuum barbs on.. i have kept these for future carb balancing needs and covered with those little rubber caps..
     
  6. peanut

    peanut XS650 enthusiast & inveterate tinkerer XS650.com Supporter Top Contributor

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    My US import 79 special ll came fitted with non- vacuum petcocks and a seperate supply to each carb although the carbs are connected together with a T tube .
    I bought some used xs650 BS34 rubber inlets off ebay for my Kawa carbs , which like yours came with vacuum take offs. I'm going to try and find a supply of rubber caps to seal mine if I can as the vacuum spigots can be useful for carb balancing .
     
  7. Demorgan

    Demorgan XS650 Enthusiast

    i got mine from Yambits.. looking a bit cracked now, but havent split in two years outdoor use in british weather..
     
  8. Signal

    Signal XS650 Junkie Top Contributor

    Peanut just use a piece of fuel line from one from one barb to the other.
     
    peanut likes this.
  9. Demorgan

    Demorgan XS650 Enthusiast

    i was wondering about that... but surely this would have the effect of weaking the mixture as air from the opposite carb (not sucking as cylinder on power stroke) would be sucked in? or would it be fuel/air mix sucked in from opposite carb?
     
  10. gggGary

    gggGary Stop that! XS650.com Supporter Top Contributor

    I now like a short chunk of fuel line with a 5/16" ball bearing shoved in it to block the vacuum ports, those rubber caps almost always crack.
    This works but it's not as good.
    DSCN7478.JPG
    Love this style clamp also but they are getting harder to find.
     
    Last edited: Jun 21, 2017
  11. gggGary

    gggGary Stop that! XS650.com Supporter Top Contributor

    It's after the butterfly so it's mix. Yamaha had a connector tube in 70-71 then quit using it.
     
  12. Demorgan

    Demorgan XS650 Enthusiast

    i see! that makes sense... i like the line with ball bearing idea too, might do this to replace them cracked hats..
     
  13. Hi Barry here I have a question. When putting kaw carbs on the xs. Do you block off the two vac ports our leave them open. Thanks Barry
     
  14. timbeck

    timbeck XS650 Junkie XS650.com Supporter

  15. peanut

    peanut XS650 enthusiast & inveterate tinkerer XS650.com Supporter Top Contributor

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    thanks signal never thought of that . I'll check it out
     
  16. pekka

    pekka XS650 Addict

    Interesting discovery about intake runner length:

    I have had issues with the engine hesitating ot "losing pull" or "falling on its face" or generally feeling that someone is cutting the throttle while riding at around 4000rpm in 5th gear. I have also complained about this earlier in this thread. I thought I fixed this with needle adjustments. Nope. Had the same issues again this summer. It turns out that my "Intake runners" (from carb outside face to air filter) were probably too long.

    I had about 9cm tube (with small flange at the end) attached to the carb and foam filter ziptied to the tube. To test a theory that the long runner might effect the slide reference air port at the carb mouth I replaced the tube with a 3cm piece of rubber hose. This cured all the hesitation. Apparently the long runner messed up the pressures near the slide or something? Also noticed that now the engine is little slower to rev-up while in neutral.

    I read somewhere that CV carbs do not like velocity stacks. Maybe for this very reason? Now I need to figure out how long runners still work so I can hide the air filters behind the bikes side covers...

    Pekka
     
    DirtyErnie likes this.
  17. peanut

    peanut XS650 enthusiast & inveterate tinkerer XS650.com Supporter Top Contributor

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    well spotted and a very useful post too. That may well help others to troubleshoot problems with their carbs.
    Now that you have made a significant alteration to the air volume and flow through the inlet you'll need to adjust the idle l mixture so hopefully you'll get your snappy throttle response back again
     
    pekka likes this.
  18. Hi Barry here I heard the motion pro know longer makes custom cables. You need to call barnetts Barry
     
  19. DirtyErnie

    DirtyErnie Renaissance Hick

    I think some of the wave tuning going on in the intake does bad things, depending on the set-up.
    The BS34 carbs HATE the K&N style pods at about the same RPM range you've mentioned, but open foam filters don't have that problem. My thought is the flat, metal end of the K&N style is reflecting the pressure wave back down the carb throat, and at that specific RPM it's causing some sort of double-carbureting action. The foam filters just let that pressure right out into the world, so there's no way to reflect the wave down the carb.

    In your case, make double sure you're not blocking off any of the air port/bleed openings...
     
    TwoManyXS1Bs likes this.

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