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Oops. I need help: Damaged Pilot screw

Discussion in 'XJ Technical Chat' started by tumbleweed_biff, Jun 4, 2011.

  1. tumbleweed_biff

    tumbleweed_biff Active Member

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    Ok, so I was working on the pilot screws of an XJ650j, and I managed to chew up the top of the screw. Can someone walk me through how to rectify this situation?
     
  2. cds1984

    cds1984 Active Member

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    Here is how I fixed mine,
    - used a tiny drill bit to create a centre hole,
    - tried to extract using a tiny ezi-out but the brass mix screw just would not hold,
    - drilled with a bigger drill until it was just a brass plated hole and used some picks and jewellers screwdrivers, as a chisel, to chip and peel the brass out.
    - then bought a matching ultra-fine(you might have the coarse threads in comparison?) tap from chacal and put that through to clean it up. Also put the tap through all the other carbs too.
    - stuck a new mixture screw in, also from chacal.

    Carbs are back in and the whole process worked a charm but was EXTREMELY painful to do and I think if I ever came across a tight mix screw again I will be heating and oiling way before I put any pressure on it after that debacle.

    I did try heating and cooling and a few other things at the ezi-out point but to no avail.
     
  3. tumbleweed_biff

    tumbleweed_biff Active Member

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    Thanks,

    I have hit it with PB a couple of times and am hoping to get to drilling and ez out tomorrow. I also have a small hand-held propane torch I can use to heat it up. Fortunately it is the #4, so I don't have t break the rack apart.

    I sure hope I don't have to go where you did ...
     
  4. Polock

    Polock Well-Known Member

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    that was soldered while the screw was stuck in the carb, i think the amount of heat to make the solder flow is what broke it loose
     
  5. cds1984

    cds1984 Active Member

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    Now that is cool!
     
  6. tumbleweed_biff

    tumbleweed_biff Active Member

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    Nice.

    So, for those of us rather unexperienced with solder, what are the steps? And what is the piece you soldered in? Looks almost like a standoff from a computer (what you mount the motherboard to) ... except that those don't have a solid top with a screwdriver slot ...

    It would seem you would:drill something of a bowl into the head of old screw, make certain of rough edges for it to grab on, fill with solder and while still melted, insert the add-on?
     
  7. mlew

    mlew Well-Known Member

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    A left turning drill bit will also work. When it grabs into the soft brass it will turn the screw out. Left turn bits can be hard to find but a good auto parts or hardware store should have them. I'll start with the smallest and drill a pilot hole them go to a larger size.
     
  8. wrxg33k

    wrxg33k Member

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    I'm pretty sure harbor freight carries left hand bits.
     
  9. Polock

    Polock Well-Known Member

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    if your not good at soldering, you'll have to be real lucky
    if there's ant kind of slot left, try to file a matching ridge in the new part, i made that one on a lathe so it had a point to match the drill hole in the screw, kind of like >>
    whatever you use needs to be "tinned" or pre-soldered, solder melted and flowed on it
    strip the carb bare, drop a tiny chunk of solder in the hole with the screw, then the hard part, heat the carb till the solder melts and add some flux when it does, this takes a whole bunch of heat to do , i used 2 torches
    when the solder in the hole melts put your new top in and try to center it and don't get burned, don't move it till the solder hardens(dab the carb body with a wet rag)
    a few other things, don't use too much solder if it gets on the threads i think all is lost, if it fails you can still use a ez-out or left hand drill, accept that this might be the end of the line for that carb
    i'am not sure i'd try it again, i think i got lucky
     
  10. RickCoMatic

    RickCoMatic Well-Known Member

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    95-Hundred Members and we can't find this fellow a Pilot Screw.

    Fine or Ultra Fine Thread?
     
  11. tumbleweed_biff

    tumbleweed_biff Active Member

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    '82 XJ650, Rick, ultra-fine. I already have the replacement, just need to get this old bugger out now.
     
  12. RickCoMatic

    RickCoMatic Well-Known Member

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    Which Carb Body is the Pilot Seized in?

    You might be better-off doing a "Body-Swap with a Carb Body from Parts.

    A desperation maneuver:
    Drill-out the Screw until there just a sleeve left.
    Pick-out the Needle, Spring and Washer.
    Drill-in, ... from the SIDE.
    Remove aluminum until you see Brass
    DREMEL the aluminum covering the Brass.
    Remove enough to set a Small Drift on the Brass Sleeve.
    Drive the Brass, folding it away from the edge.
    Grab with Needle Nosed and muscle-out.

    Clean-up.
    Thread a Bolt with Matching Thread into the Pilot Hole.
    Prep the Bolt.
    Threads smeared with grease or antiseize
    Two layers of Teflon Tape

    JB Weld side hole
    Cure
    Remove prepped bolt after JB Cures
    Re-Tap

    Have a Swap Body standing by.
     
  13. Robert

    Robert Active Member

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    If needs be you can shoot the carb body to me and I'll get it out.
     
  14. autosdafe

    autosdafe Member

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    Is it really all that bad to seperate the bodies?
     
  15. Robert

    Robert Active Member

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    Not in my opinion. That applies only to the Hitachis, I don't know jack about the Mikunis.
     
  16. autosdafe

    autosdafe Member

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    The manual says don't do it to the mikunis but it's because you have to properly align them. Not really hard to do. Just lay them on a flat surface
     
  17. chacal

    chacal Moderator Moderator Supporting Vendor Premium Member

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    The safest way to handle un-removable mixture screws is:

    "the trick to removing them safely is to be able to drill into them straight, so you don't get into the carb bore threads (then it's game over!).

    My best advice....and what we do......is take the rack to a local machine shop, and let them precisely jig it up onto their fancy CNC drill press, so they can get dead-nuts accuracy is drilling thru the center of the screw, and then easily EZ-out it or use a left-rotation drill bit to twirl it out.

    It's a 5-minute job with the right tools, something that can be done during their smoke break. Take a $20 bill with you to grease the wheels of progress."
     
  18. Robert

    Robert Active Member

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    +1^^^ Our machinist is top notch and does incredible work!
     
  19. tumbleweed_biff

    tumbleweed_biff Active Member

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    Hmmm, I don't know any machinists,. but I will see if can track one down. I do know someone who is quite handy with solder ...

    Tell me what you think of this: carefully apply JB weld to top of screw. Due to nature of chewed up top, has nice rough surface for adhesion. Then, attach an extension screw with a better top and allow to cure. Twist out. Basically the same idea as the solder method but using JB weld instead.

    Rick, carb body is #4 so is on the outside and easilyt accessible without removing from bike.
     
  20. RickCoMatic

    RickCoMatic Well-Known Member

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    No.
    Separating the Bodies is only Labor Intensive.

    When the Bodies are separated you have to reposition a great many Spring-loaded items to reassemble the rack.

    Its TIME consuming.
    Once the Rack is reassembled, with the fasteners tight enough for allowing the bodies to be repositioned, ... slightly ...

    Place the four on the side of a New 4-foot Level.
    Bump them with a light Rubber Mallet.
    Once they are Leveled tighten the Fasteners.

    The trick is getting them back together in the frames.
    Once the farames are back-on, ... you arent too far "Out" that leveling them and bumping them level and plumb won't correct.
     

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