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REPETE'S XS650B Preservation Carburetor

Discussion in 'The Garage' started by REPETE, Oct 31, 2019.

  1. REPETE

    REPETE XS650 Enthusiast XS650.com Supporter

    Hello All
    With a couple of stumbling blocks behind me (most recent being some air box questions) I am so very close to having this ol' girl road worthy after 20+ yrs. of sitting.
    Currently, I'm challenged with two issues.... which I'm hoping #1 solves #2.
    We'll see, so I won't get into that yet.
    Present issue I'm tackling is that the right side carb isn't functiong below 1800 +/- rpm.
    So, pilot jets, right?
    Last night I have removed the right side carb to revisit all that I had done in my rebuild and clean, clean and clean some more. I found no visable signs of anything previously having been assembled incorrectly. All parts used were Mikuni and all were to stock specs (pilot & main). I studied my float heights from numerous angles to be sure I measured accurately. All jets have been probed with fine wire to see if there was any remaining debris. All were clear and I can blow air through. But, there is one small one on the bottom of the main body that is the end of a tube that runs vertically through the throat of the carburetor to the inside of the carb top. I can run a probe up in it the full length but Im not sure if I'm blowing air through it or not. I don't know where that exits (enters) to atmosphere so I can check it. I may be fine, but I'd like to know more about it before I button back up.
    Also, in the pics youll see that the nipple for one of the "crossover" tubes pulls out of the carb body. It's snug, but I don't know if just snug is good enough.
    Should AI be looking to get this adhered in place?
    If yes, any preferred method?
    All advice welcome.

    Pete

    IMG_4818.jpg IMG_4819.jpg
     
  2. gggGary

    gggGary Stop that! Top Contributor XS650.com Supporter

    On the cross over I'll put a bit of rubbing compound on it chuck it in a cordless and lightly spin in body, clean well, use bit of super glue, tap in place. On the vertical tube: spray carb cleaner in the end. On running issues. Note my recent posts in WJL thread.
    Short list;
    Throttle shaft seals
    Proper synch; retract idle stop screws, check no air ( light) visible around butterflies. Be sure butterfly idle screw opening AND cable pull match side to side.
    Then I think this was the biggie on mine remove polish lube advance shaft,
    set points with correct procedure. Check condensers.
     
  3. 5twins

    5twins XS650 Guru Top Contributor

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    That nipple that pulled out is for a fuel crossover hose. It may leak gas if not sealed up properly. After Gary's cleaning advice, I might try a little Yamabond on it. The hose looks old, shrunk, and is probably hard as a rock. Might want to replace that with some fresh stuff. It's so stuck on the nipple now, that's what probably pulled it out in the first place.
     
    gggGary likes this.
  4. REPETE

    REPETE XS650 Enthusiast XS650.com Supporter

    gggGary: "remove polish lube advance shaft"
    This would affect non function at idle speed? If I manually "blip" the right carb throttle she'll sometimes give a "pop" but will always catch and run beautifully.
    The plug always has spark (although I've seen better).
    However, given the age and the fact I'm trying to attend to everything I will definitely remove that shaft, clean, polish and lube. At this juncture seems like I've done every other moving part, so may as well run the table! :laugh: Hopefully it's not a major undertaking.
    I'm also guessing that all my points and timing settings are about to be negated :umm:
    I will also check butterfly seating for daylight around edges while it's on the bench but my recollection is that it is solid... no play whatsoever and was seating nicely.

    5T: Bingo! The hose is hard as a rock and that's exactly the cause. The new tubing I have on hand looks (at a glance) to be too large.
    Do you know (of course you do :laugh: ) the proper size? In the past I've found that anything my local auto parts store has in the way of hoses (all std. sizes) have never given me a satisfactory fit.
     
  5. gggGary

    gggGary Stop that! Top Contributor XS650.com Supporter

    Ps this supplies emulsion to idle mix circuit.
    2019-10-31 14.11.36.jpg
     
  6. gggGary

    gggGary Stop that! Top Contributor XS650.com Supporter

    Advance shaft no it shouldn't effect points though it doesn't hurt to recheck.
    Turn crank so pin on RH Side points up. Remove rh 10mm nut, tap work shaft out past points, you don't need to remove the points cam from the shaft.
    Forget auto parts, local small engine dealers stock this
    20191031_142036-1.jpg
    Works for all your fuel lines, private labeled tygon.
    Use spring clips.
    79BS38s.jpg
     
    Last edited: Oct 31, 2019
  7. gggGary

    gggGary Stop that! Top Contributor XS650.com Supporter

    I'm also pretty big on new float valve, seats on all my carb overhauls. Leaking valve causes very rich idle.
     
  8. REPETE

    REPETE XS650 Enthusiast XS650.com Supporter

    Brand new along with the o-ring. Only original pieces are the needles and the diaphragm float which passes the visual inspection and "slow drop test".
     
    gggGary likes this.
  9. REPETE

    REPETE XS650 Enthusiast XS650.com Supporter

    Great tip on small engine supply!!!!
    I'll stop in there tomorrow.
    Hopefully they'll have the spring clips as well
     
    gggGary likes this.
  10. gggGary

    gggGary Stop that! Top Contributor XS650.com Supporter

    Ps I don't think those are 71 carbs, 74-75 mebbie? With the one choke and cross over tube, that "other" crossover tube being sealed is also critical. Could introduce major air leak.
    Note idle emulsion is supplied by pilot jets, make sure both pilots are correct BS30/96 Style.
     
    Last edited: Oct 31, 2019
    peanut and TwoManyXS1Bs like this.
  11. REPETE

    REPETE XS650 Enthusiast XS650.com Supporter


    Possibly this may be part of the problem ?????

    That's the orifice I was referring to. It's the end of the tube that passes verically through the carb throat, correct?
    If I blow air into it, where should I feel it coming out? :umm:
     
    gggGary likes this.
  12. REPETE

    REPETE XS650 Enthusiast XS650.com Supporter

    OOPS!!!! '75 XS650B
    editing thread tittle now

    :banghead:
     
    gggGary likes this.
  13. 5twins

    5twins XS650 Guru Top Contributor

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    The inlet Gary circled in his pic is where the pilot jet fuel/air mix is fed into the carb. From there, it exits into the main bore through these 4 tiny holes .....

    [​IMG]

    The 3 holes clustered together at the top come directly from that inlet hole. The one off to the side also comes from that inlet hole but passes by the mix screw first. The amount it flows can be adjusted by the mix screw. So, you'll need to dribble or spray some solvent or carb cleaner into that inlet hole, then blow it through with compressed air and watch for it to come out the 4 holes. I start with something mild like WD40. If it blows through then fine, if not I resort to something stronger like carb cleaner. If I do have to resort to carb cleaner, I flush it out afterwards with WD40 to wash any remnants out.
     
    gggGary likes this.
  14. 5twins

    5twins XS650 Guru Top Contributor

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    This works best if you remove the mix screw because it is partially or mostly blocking that one hole into the main bore when in place. You'll then need to hold a finger over the mix screw hole on the outside of the carb body or most of the cleaner will just blow out it. Then you can alternate blocking off some holes to direct the cleaner just out certain others. Block the mix screw hole on the outside of the carb and it's corresponding single hole inside the main bore, and the cleaner will be directed just out the other 3 holes. Block those 3 holes and the cleaner will be directed just out the mix screw hole. You can do a "back flush" too. Block off the 4 holes inside the main bore, put cleaner in the mix screw hole, blow it through, and it will come out the inlet hole on the bottom of the carb.
     
    gggGary likes this.
  15. REPETE

    REPETE XS650 Enthusiast XS650.com Supporter

    GREAT INFORMATION!

    I have a direction....
    I will attend to the Advance Shaft
    I will clean & polish the nipple and adhere it into the carb body.
    I will revisit and verify the butterfly condition
    I will ensure that I'm getting a flow through those pilot holes and the mix screw hole hole.
    I will get into see my local small engine dealer
    And I will report back later in weekend when through.

    Thank you gentlemen!

    I'm close. So, very close! :)

    Pete
     
    peanut, Mailman and gggGary like this.
  16. REPETE

    REPETE XS650 Enthusiast XS650.com Supporter

    Got it!
    I'm on it!
     
    gggGary likes this.
  17. grizld1

    grizld1 Grumpy old man Top Contributor

    The "tube" you keep referring to is the needle jet (AKA "atomizer," AKA "emulsion tube"). Don't get aggressive with it. It's the major metering component in the cruising range of the throttle, and a one-number step indicates only a .0002" difference in size of orifice. Gary hinted at this, but here are some stats to back him up: According to a poll conducted by the American Association of Shadetree Mechanics, 80% of reported carburetor malfunctions originated in the ignition system, 10% were due to absence of fuel, 3% originated in the valve train, 3% were due to cylinder condition,and 1.5% were due to lubrication failure.
     
    Jim, thuban, GLJ and 1 other person like this.
  18. REPETE

    REPETE XS650 Enthusiast XS650.com Supporter

    Thanks
    This is the tube I was referring to.....

    IMG_4827 (1).PNG
     
    gggGary likes this.
  19. grizld1

    grizld1 Grumpy old man Top Contributor

    Yep. The needle mounts in the slide and hangs down into the needle jet. If you click the Tech button and browse a little you'll find a link to the Carb Guide that 5twins and I wrote back when Hector was a pup. In it you'll find a bunch of 5t's very fine labelled photos.
     
  20. 5twins

    5twins XS650 Guru Top Contributor

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    Actually, I think he means that long brass tube running top to bottom back in there behind the needle jet. I don't think that has anything to do with fuel flow, I think it's a vent of some sort for the area above the diaphragm.
     

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