Drilling and Tapping JB weld

Discussion in 'Motorized Bicycle General Discussion' started by fischer550, Oct 19, 2014.

  1. fischer550

    fischer550 Member

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    A friend of mine stripped his female exhaust holes, tried to drill and tap to M8 but he did that wrong too, and he screwed that up too. I have filled his holes with JB weld (which it says can hold constant temp of 500 degrees) and after 24 hours am planning on correctly drilling and tapping the jb weld holes back to M6. will it work?
     
  2. maniac57

    maniac57 Old, Fat, and still faster than you

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    In a word, no. JB weld will fail under motor mount stress. It might hold a minute, but vibration WILL get it soon.
    Much better idea is to tap it out larger to reach undamaged metal.
    Or a Helicoil if possible. This fixes threads stronger than new.
     
  3. Davezilla

    Davezilla New Member

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    I'd go the helicoil route myself... the JB won't hold under that kind of stress for long...
     
  4. Kioshk

    Kioshk Active Member

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    What they say....don't even waste your time. Helicoil!

    Edit: you might consider a slip-connection on the pipe. I have a Voodoo expansion pipe, and the interface with the head is basically 1-inch of exhaust-pipe out of the head connected to the rest of the exhaust system with a copper plumbing nipple. The expansion portion is kept in place under passive tension...I use bailing wire to keep the pipe from falling out. Others use springs. This eliminates a lot of vibration imparted by a rigid exhaust system, and greatly reduces the forces on the exhaust-port studs. Theoretically, you MIGHT get away with epoxy, but you'll have a better chance with inserting thin wire or metallic strips into the stripped stud-holes and muscling the studs in. This in conjunction with the slip-connection will work while you save up for a helicoil kit.
     
    #4 Kioshk, Oct 20, 2014
    Last edited: Oct 20, 2014
  5. Davezilla

    Davezilla New Member

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    Yes, the slip fit connection on 2 stroke exhaust systems is the way to go if you can do it, it's been around about as long as 2 stroke engines and it's Very effective as the heat expansion of the inner pipe causes a seal for the outer pipe, and when things cool down there's no stress on the system especially at the exhaust port studs.
    Now Treatland.tv has some rather cool ball joint fittings that one could connect at the head and then weld on the rest of the system which also alleviates this stress at the exhaust port and gives your system a flex point where it can flex instead of crack under stress or vibration, or both.
    Not that it's needed on every system, but something else to consider when building a modded system.... the slip fit method is old and tried & true tho and ya can't go wrong there on a stock or modded setup.
     
  6. highstrung74

    highstrung74 New Member

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    replace the jug for 25.00 and be done with it and have a fresh topend while at it...might wanna do the rings while apart jus cause your in there... dnut
     
  7. KCvale

    KCvale Active Member

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    A new cylinder and rings are like $12, why spend more than that on a so-so fix when you can have a new top end with pristine exhaust mounts?
     
    #7 KCvale, Nov 16, 2014
    Last edited: Nov 16, 2014
  8. Rollingstones

    Rollingstones New Member

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    i just heli coiled mine today and bought some 1/4 x 20 hex bolts and it is more secure now then it has been on my 2 builds. Did the same to my engine bolts and they have held up beautifully.

    I prefer to just go pick up a $6 tap and thread kit at auto zone and bolts from home depot and get it done right away

    Getting to do things myself is half the fun, and also I don't have to wait for anything to ship which is nice because patience is not one of my virtues :)
     
  9. Davezilla

    Davezilla New Member

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    Yes, new jugs are cheap, but if someone spent a lot of time porting and milling on one and a stud boss cracks or strips out I don't think they would want to scrap it and have to start over, not to mention another break in period as well when a simple helicoil can fix the problem without even needing to disassemble and in some cases, no need to even remove the engine from the bike.
     
  10. KCvale

    KCvale Active Member

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    ...they wouldn't have been foolish enough to strip or bust a stud off in the jug.

    I've done my share of oversize drilling and tapping and helicoiling stripped motor mount holes but a no brainer to just replace a compromised jug but hey, to each his own, just count up all the parts and tools and your time to maybe get it re-drilled perfect and weigh that against just a new good jug.
     

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