Head Stud Repair

Discussion in 'Tech Area' started by toasterknight, Aug 3, 2014.

  1. toasterknight

    toasterknight New Member

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    Just finishing a rebuild on my K1 CT70. I went to torque down the head and the top left stud (bike's left) pulled the studs clean out. I'm concerned that using a helicoil would cause the wall of the hole to be to thin and do the same thing over again. Does anyone have any suggestions as to a way to fix the stud without replacing the crank case half?
     
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  3. bc17a

    bc17a Well-Known Member

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    A helicoil is what I would use. The repair doesn't require much material to be removed and will be much stronger than the original case so not to worry about it being too thin.
     
  4. fatcaaat

    fatcaaat Well-Known Member

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    Depending on your level of expertise, and how much you feel like tearing a motor down to complete a repair, I'll offer up a cople of solutions that might work out for you.
    1. Helicoil or time sert or similiar. These work out great, require little in terms of skill to complete and are a great repair. If the threads have pulled it works fine, if the case cracked, this isn't your best option.
    2. Fill with JB weld or Marine tex gray and drill/tap. This works whether or not the case is cracked.

    Those two options only require you to pull the top end off.

    3. Fill/drill with low temperature aluminum rod. This works ok, but if the case is cracked, means you need to actually open up the crack more and allow the metal to seep in.
    4. Weld it and drill tap...if you have someone that knows what' they are doing, this is obviously the best fix...and probably the most expensive.

    I have done them all...and they all work fine. As a matter of fact, I am using option 2 right now on my 88cc Hammerhead engine. I filled with a product called Marine Tex gray, drilled and tapped it, and let it set for a week. Then I added blue locktite and turned the stud in and let that sit for a day. Working perfectly fine right now. No issues...it's all about the prep.
     
  5. kirrbby

    kirrbby Well-Known Member

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    If you use the JBweld be sure to allow plenty of time for it to set up.
     
  6. OLD CT

    OLD CT Well-Known Member

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    Using jb weld would not happen here. If it cannot be done with a helicoil or timesert refilling/tapping with a tig weld. I would most certainly live with the replacement engine number rather than redoing it later when it fails. Especially when you can buy a good used case for 30 bucks plus shipping. Too many vibrations in that area to make a good dependable repair with jb. That's my thoughts,yours may vary.
     
  7. fatcaaat

    fatcaaat Well-Known Member

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    I currently have used Marine Tex gray successfully to seal the water jacket holes (12 of them) on my Jeep 4.0 L head that was put on top of a 4.2L bottom. It's been that way now for 12 years and 70k miles. It is certainly not the best repair you can make on an engine case, but it will work great if you are meticulous about prep and approach. However, if the case is not cracked...it is just a thread pull, Helicoil is really the way to go.

    One more option that will ensure an incredible fix but is more permanent, meaning that stud isn't going to come out is to do as I suggested with the marine tex gray or the cold weld product that has granulated metallic powder (not JB weld) and fill, drill, tap as suggested. But then, instead of blue locktite, put in Bearing Lock for close tolerances and thread that sucker in your hole. It will never come out but is pretty much guaranteed to ruin your cases if you ever need to take it out later. It requires 500 degrees to release it...and that means probably something like 600 to the cases, which isn't good for them.
     
  8. Enginedoctor

    Enginedoctor Well-Known Member

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    lots of options given here... aside from a crack, i second the heli-coil 6mm repair. make sure you back the tap out 1/2 turn for evert 3/4 turn you make with it. it's tedious, but if you don't it comes out all choppy. i usually do about 2-3 turns, slowly, then remove it completely, clean the shavings off of it, then start over again. the first couple turns you make are the most important. if you don't back it off regularly, you'll wind up with a sloppy hole. Also, if the inserts are really short, i have no issue putting one insert deep inside the hole and then butting another up against it towards the outside. as long as you don't overlap them, you won't have any trouble. this means there's a full length of SS threads inside of your freshly tapped slight oversize aluminum hole. should be stronger than stock, believe it or not....

    hope you're using an inch pound torque wrench on those head bolts, btw...
     
  9. toasterknight

    toasterknight New Member

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    Thanks for all the advice. it just pulled the threads so i will probably just have the local atv shop put in a helicoil. i was using an inch pound torque wrench at 112 inch pounds.
     

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