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Carb Questions

Discussion in 'XJ Technical Chat' started by troym204, Aug 21, 2017.

  1. troym204

    troym204 Member

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    So I have finally gotten around to getting into the carbs, right now I have #1 taken apart, the other three intact and racked as a reference.

    I am following my Yamaha service guide as a reference, and taking pointers from the church of clean.

    IMG_1091.JPG
    What is the flat head nut next to the Starter Plunger opening at the bottom of the photo, should it be removed and cleaned?

    Also what are the two golden nuts (they look similar to the Pilot and Main Jets, they seem to be on the other end of the same passage) in the vacuum chamber? Should they be removed and cleaned, or should they just be probed clean?

    IMG_1092.JPG
    I also can not find a reference to what this (brass piece?) is in the back of the photo, it looks bent to me (slightly to the left), it looks like its fixed to the carb body itself (cannot be removed but could be wrong).

    What is it, and is it a problem that it is bent. If so what is my best course of action?

    Thanks, Troy.
     
  2. Jetfixer

    Jetfixer Well-Known Member

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    Your first question that is the pilot jet yes needs removed there is an O ring on it and a small spring so don't loose it. the other 2 jets need pulled out make a note of location . While carb is split from rack remove butterfly plate and shaft to replace shaft seals ( xj4ever has them) Soak carb is what I recommend Berrymans Carb cleaner 1 gallon container submerge carb one at a time for about 1 hour , then clean in hot water and dawn dish soap , this should get carb clean , and reassemble . The bent tube is what goes into the fuel enrichment in the float bowl. Carefully try to straighten is about all you can do. Cheers
     
  3. troym204

    troym204 Member

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    Great info, thanks.
     
  4. Plug

    Plug Active Member

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    The other two jets.....assuming h33 carbs....big bottom hole goes in the hole towards the front of the carb body, little hole jet goes in the second....there is also a tiny washer that goes between the spring and o ring on that mixture screw.......I have been able to get by on the last two racks I split by just replacing that idle o ring, it's washer, the throttle shaft seals and the fuel o rings. There is also jets in the back of the carb facing the air box that can come out as well before soaking.
     
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  5. Plug

    Plug Active Member

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    Order a set of butterfly screws as well.......on the xj550, I had to grind them to get them off, while with the 750 seca, which the carbs have never been off of, they simply came out with a screwdriver.
     
  6. k-moe

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

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    That would be because of the carbs being made by different manufacturers. Mikuni peened the ends of the threads, Hitachi used thread locking compound.
    Replacement screws are a good thing to have regardless. Some will get messed up, and I usually lose at least one on the floor.
     
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  7. Stumplifter

    Stumplifter Well-Known Member

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  8. Jetfixer

    Jetfixer Well-Known Member

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    I upgraded to allen bolts ... looks kool!!!
     
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  9. k-moe

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

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    One-time use items at this size though. The heads (no matter who makes them, or how good of a wrench you have) tend to waller out upon removal.
    They are easier to get into place than either crosshead or flathead screws.
     
  10. troym204

    troym204 Member

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    I'm not following. What was it that you had to grind off?

    Edit: I believe I know what your talking about now, the screws holding the butterfly onto the throttle shaft, correct? I luckily had no problems removing mine!
     
    Last edited: Aug 21, 2017
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  11. troym204

    troym204 Member

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  12. k-moe

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

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    Correct. The Mikuni carbs (on the 550) had the threads peened, and have to be ground or filed in order to be removed. Thankfully Hitachi chose to not use that method of screw retention. Be sure to use a medium-strength thread-locking compound when reinstalling the throttle plate screws.
     
  13. troym204

    troym204 Member

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    Some more questions:

    IMG_1110.JPG
    Throttle Shaft Diaphragm #1 has a pinhole sized puncture (not shown in picture).
    What is the best method of "repairing" this, or would it be wise to purchase new?

    IMG_1134.JPG
    The Needle Jet or Emulsion Tube is showing wear.
    Its been cleaned up as you can see, should I replace?

    IMG_1151.JPG
    So the clumsy; yet industrious PO of the bike has done a nice little repair.

    IMG_1152.JPG
    I started to pick at what I thought was gunk, but instead was RTV or some sort.
    This is where the pin holding my floats in place calls home, things seem to line up nicely.
    Does it seem like a serious issue to anyone if I just secure it back in place?
     
  14. Polock

    Polock Well-Known Member

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    just so we have the same page: grind off the back threads, not the screw head
     
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  15. Polock

    Polock Well-Known Member

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    a Diaphragm might be expensive, try a tiny dab of RTV after you clean it.
    the Needle Jet can ware oval where the needle goes in it, otherwise that looks good
    how tight a fit is that pin in the hole? could you smash the pin enough to make it a little tight? then butter it up with jb-weld and hop for the best.
    look for a used carb rack for parts
     
  16. Jetfixer

    Jetfixer Well-Known Member

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    You can repair small holes in diaphragm with a condom or rubber glove and rubber cement . This actually works !!!
     
  17. fiveofakind

    fiveofakind Well-Known Member

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    Isn't a rubber glove the same thing as a condom......:)
     
  18. hogfiddles

    hogfiddles XJ-Wizard, Host-Central NY Carb Clinic Moderator Premium Member

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    Sort of--- one goes over your HAND
     
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  19. hogfiddles

    hogfiddles XJ-Wizard, Host-Central NY Carb Clinic Moderator Premium Member

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    But the carb shown is a hitachi
     
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  20. XJ550H

    XJ550H Well-Known Member Premium Member

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    po would not be the first one to fix float post some jb weld would have been better than rtv, there are a few threads on this subject
     
  21. troym204

    troym204 Member

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    The bike was running; albeit rough when I got it so I figured as much. Definitely agree with the JB weld.
     
  22. hogfiddles

    hogfiddles XJ-Wizard, Host-Central NY Carb Clinic Moderator Premium Member

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    And won't be the last one to have the jbweld dissolve in the gas
     
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  23. XJ550H

    XJ550H Well-Known Member Premium Member

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    jbweld gastank repair epoxy ? but do agree a new body is the best way to go.
     
  24. Nuch

    Nuch Well-Known Member

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    Yeah, he went there... LOL
     
  25. Stumplifter

    Stumplifter Well-Known Member

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    Thought Polock (or was it you Dave?) posted a rather professional float post repair picture not too long ago?
     
  26. hogfiddles

    hogfiddles XJ-Wizard, Host-Central NY Carb Clinic Moderator Premium Member

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    Not me-my way of float tower repair is:

    Get another carb body that ISN'T bork
     
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  27. Polock

    Polock Well-Known Member

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    is this the one
    [​IMG]
    you have no idea what a p.i.t.a. that was
     
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  28. Nuch

    Nuch Well-Known Member

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    Is that a Dove tail? OMG!
     
  29. k-moe

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

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    Yes it is. I was clarifying the differences between the two, and the need for threadlock, after another member mentioned needing to grind the screws (not necessary on Hitachi carbs).
     
  30. hogfiddles

    hogfiddles XJ-Wizard, Host-Central NY Carb Clinic Moderator Premium Member

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    Ok :)
     
  31. Jetfixer

    Jetfixer Well-Known Member

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    Liquid steel is fuel proof it is a two part you kneed it together and push it in place it sets up in about 5 minutes . I have used it to repair my engine case on my VW Beetle and a carb intake it has lasted 6 years.
     
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  32. Stumplifter

    Stumplifter Well-Known Member

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    Yea - that's it - Professional Installation Technique Award.

    Sure maybe it was a pain, but such a beautiful thing to look at.
     
  33. Polock

    Polock Well-Known Member

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    i still have it, if you want to buy it :)
    i'll even throw in the dried up gasket :D
     
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  34. MattiThundrrr

    MattiThundrrr Not a guru

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    Have I been using them wrong? Is this why I have 2 kids?
     
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