JB Wield

Discussion in 'Motorized Bicycle General Discussion' started by AnthonyX99, Mar 12, 2010.

  1. AnthonyX99

    AnthonyX99 New Member

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    Hey guys been awhile since I posted here. The back of the engine, the studs pretty much snapped and I can't tap it because there's no space at all I need a m7 stud and thats not going to work. Now for my question if I applied Jb wield to the engine and stuck the spacer on it along with the new steel pipe I'll be using I'll be using it on the pipe as well, Will JB wield be able o take the vibrations and not crack or just fail all together?
     
  2. bandito

    bandito New Member

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    From experience fix it right. For every 1 success Ive heard Ive seen 6 failures in trying to repair something with JB weld. It has its purpose but not in a fix for a part you depend on. Thats my take.
     
  3. AnthonyX99

    AnthonyX99 New Member

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    I forgot to add the engine will be sitting on two steel plates side by side set vertical so it wont be floating.
     
  4. bairdco

    bairdco a guy who makes cool bikes

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    i doubt it would work. and for the amount of effort you're going to put into something that will probably end in failure, i'd take the engine to a machine shop and have them get the snapped studs out for you.

    then, i would figure out why they snapped in the first place, and fix that (without JB welding anything.)
     
  5. Earthman

    Earthman New Member

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    JB Weld isn't nearly as strong as cast aluminum (see attached typical properties of AL vs JB Weld). However, might work in some applications as a filler in a confined space, but not with heavy or repeated loading; i.e., vibration. In any case, I agree with removing broken stud(s) and replacing.

    JB Weld's website: J-B Weld Company - J-B WELD Product Information
     

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    #5 Earthman, Mar 12, 2010
    Last edited: Mar 12, 2010
  6. caprirs302

    caprirs302 New Member

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    JB weld is crap, the only thing I ever had success with while using JB weld was welding a friends locker shut back in high school.....


    I just removed a snapped off stud from my motor today by using a rotary tool with a cutting wheel and cutting a little slot into the stud. Then it came out with a screwdriver quite easily.
     
  7. rockvoice

    rockvoice New Member

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    thats awesome, i wish i would have thought of that in high school
     
  8. civlized

    civlized New Member

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    Boy oh boy, Anthony. In case you didn't notice, JB mentioned around here is like calling someone's mom a colorful term! With that out of the way, I've had a lot of success with JB STIK and similar products. NOT THE 2 LIQUID TUBES. I've had success with the liquid, when used for it's purpose, but the stick putty type work great, again, for their purpose. I will have to agree that JB, in most cases, should not be used for a permanent repair in this type of application. You are asking for failure and wasted time. I will use it in a split second to do a quick fix for something temporary or some not so important fabbing, like rear view mirror mounts or something. Just my $.02. Best of luck getting it repaired.
     
  9. aspireonescs

    aspireonescs New Member

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    thanks for that info, brings a fresh light into my eyes :)
     
  10. mountain80

    mountain80 New Member

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    JB weld is not good for extension stresses. Get it meaured, weld and re drill.
     
  11. AnthonyX99

    AnthonyX99 New Member

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    I could just get a aluminum plate wielded on the cast by a machine shop and pre drill the holes and bolt the pipe on would this method work better, I don't know if the alloy cast would melt but that should hold. I cant retap because the hole to big already.
     
  12. BarelyAWake

    BarelyAWake New Member

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    Hmm... ya might be able to tap - just one size larger is all, sometimes going the next size up using SAE instead of metric will do the trick... but I dislike "hybrids" of standard & metric (not that I've much of a choice w/my build heh).

    Another option for an oversize that ya want to use the original size fasteners are Heli-Coil inserts, they're a bit costly but handy to have... I'd just tap one size up tho 'cause ya hafta w/a Heli anyway.

    Welding to the cast aluminum these engines are made of is... dicey. It can be done by a welder w/real skill - but yer runnin' the chance of blowing a big hole in the case and/or havin' beads that just won't hold :(
     
  13. Bikeguy Joe

    Bikeguy Joe Godfather of Motorized Bicycles

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    JB Weld is the shizziola....when use correctly and for it's intended purpose. It is not a cure all.
     
  14. cigron

    cigron New Member

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    If your stud is 6mm. A 1/4 in thread tap will go in A 6 mm hole and tap out the hole
    and use 1/4in bolt or thraeded rod right. I fixed my head and cylinder and barrel.
    .I took A bolt about about 2 inches
    longer then the stud,i took out put A nut A lock washer A nother nut lock washer
    and A flat washer. tightend it to ten foot pounds.then cut the part of the bolt
    that was left sticking up in the air.It works just finedance1
     
  15. Retmachinist

    Retmachinist New Member

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    The only problem I have ever had with these Chinese engines is the rear mounting studs breaking do to the vibration. Now the first thing I do before I even install the engine is drill and tap the two rear holes to 8mm and use grade 8 cap screws. I have never had one of these fail no matter how bad the vibration. These motors are such a crap shoot on the vibration. It does seem like the last few engines I have purchased have been alot smoother. Maybe they have done something as far as the quality control?

    John
     
  16. BarelyAWake

    BarelyAWake New Member

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    It's impossible to tell w/o lookin' at the bike... but I doubt the vibration from a properly mounted engine running would be the cause with most fastener failure. Here's what I've seen to be the most common causes;

    Attempts to soft rubber mount.
    Incorrect torque.
    Gradual over-tightening of fasteners by "checking torque" w/o a torque wrench.
    Failing to use lockwashers.
    Frame damage/mismatched mount radius.
    Neglect and/or improper installation.
    Rear sprocket not being centered.
    Damaged rear wheel, out of true/sloppy bearings
    Slack chain/tensioner/misaligned sprockets.

    I'm sure there's other causes as well - but the above are defo the most common. There's some truth to the claim that the hardware itself is substandard - but given my aluminum Schwinn has thousands of miles on it with the stock "rag joint" sprocket, all stock fasteners, and even has a drilled D tube (that IS a sketchy lol) and has survived a buddy's EPIC crash as well as the relentless abuse by yours truly... Given there are far more people that haven't had engine mount issues than people who have...

    I've no choice but to suspect other causes ;)
     
    #16 BarelyAWake, Mar 14, 2010
    Last edited: Mar 14, 2010
  17. bairdco

    bairdco a guy who makes cool bikes

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    i agree with Barely.

    i swap out the hardware for 6m socket cap screws, tighten them down once, check them a few days later, then forget about them. every now and then, just for the heck of it, i check them again, and have never needed to tighten them. by "check," i mean i put an allen wrench on them and see if they'll turn. if they don't, i don't try to make them.

    i also remove mine dozens of times to do different modifications, and never had one strip, seize, snap, or anything other than come out like they're supposed to.

    and i use anti-seize on the threads. loc-tite and JB weld are not allowed on my bikes.
     
  18. 2door

    2door Moderator
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    The last three posts should be carved in stone somewhere. Heed the advice from Barely Awake, Retmachinist, and Bairdco and you can't go wrong...and stop 'tightening' your fasteners every time you ride. That's the worst advice given here. Save the J-B for model cars and toy airplanes.
    Tom
     
  19. TheE

    TheE New Member

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    Mabye you could drill into the snapped stud and JB weld a rod into there so you can unscrew it?
     
    #19 TheE, Mar 14, 2010
    Last edited: Mar 14, 2010
  20. BarelyAWake

    BarelyAWake New Member

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    >.>
    <.<

    psst - I found bairdco's secrut ingredient :D

    [​IMG]
     

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