Freeing frozen valve cover bolt with a welded nut...

[Guest]

Well, my last post was about my new-to-me 1982 GS1100GZ on which I'm

working to replace a leaky valve cover gasket as well as check the valve clearance. One of the stainless steel bolts securing the cover was stuck, and I applied too much pressure such that I broke the top off half inch off of it. Fortunately I was able to get the valve cover off with the one bolt still in the cylinder head, such that I now have about 3/4th of an inch sticking up. I can get vice grips on the shaft, but with the hex head off can no longer use a socket set on it. When I try with the vice grips I still can’t get it loose.

I tried applying heat (and got good advice on how to do this in the previous post thanks), but it did not fix the problem, and I still was not getting good grip with vice grips (I also tried to saw a notch in the top of the bolt to use a screwdriver, and this did not work). So I'm moving on to welding a nut to the top of the stud.

A couple of questions on this. Should I weld a nut on that is basically the size of the stud (the O.D. of the stud (not the head, which is of course no longer attached...) is 5mm, should I use a nut with a similar I.D? Or should it be larger so there is space between the inside of the nut and the outside of the bolt? Also, am I correct in understanding the nut should be large enough to go around the stud, as opposed to a smaller nut welded on the top of the stud? I have about 3/16th of the stud sticking up from the engine head, which happens to be the same height of a standard nut for a bolt this size it seems. Lastly, if I drill out the stud first so more weld can adhere creating a stronger bond, how wide and how deep in the bolt should I go with this hole? Thanks for any thoughts from those that have done this previously!

[Grimly]

Welding a nut on is often successful as a means to extract the broken part, as the heat from the welding works its magic on the thread corrosion further down. It's more localised and intense than the flame was.
A 6mm nut would be the size of the original thread, but I might be inclined to weld on an 8mm nut just for the extra grip area it provides and the larger nut is less prone to deforming with the weld heat. If you position it so it's sitting halfway on to the remaining bolt it means you can fuse the bolt metal with the nut as much as reasonably possible without wrecking it.

[Fxvielander]

Well I successfully welded a slightly oversized nut onto the stud, and got a good bond between the two. I gently then tried to wrench the bolt out of the cylinder head, and the original bolt shaft again broke, this time in a new place. Now there is somewhere between an eight and a quarter of an inch stud sticking out of the head.

Should I keep welding nuts on to the remaining stud? I’ve heard if the stud breaks off below the level of the cylinder head (so is no longer visible) you can weld until there is material sticking above the surface so you can then attach a nut to wrench on. Can I just keep doing that hopefully without damaging the head (which the weld material will not stick to, right?)? My fear is the bolt is just going to keep breaking every time I get a new nut on.

Thanks for any advice here!

[posplayr]

You have to slowly work the bolt back and forth but do not excessively twist the bolt.. If you just crank on it it will snap off as you see. Especially true with stainless that is more brittle.

With such a short numb you are getting close to the left handed drill technique.

[chuck hahn]

As Jim said and use lots of penetrating oil.

[Fxvielander]

Thanks, will try as you both suggest. Bought some left handed drill bits, but this particular stud is under the bike frame so a drill can’t be positioned properly since the frame is in the way. I have a Dremel tool with a right angle attachment, and was going to try the left handed bits with that until realizing the tool has no reverse setting, so the bits wouldn’t be rotating in the right direction. Let me know please of any words of wisdom, thought best to perhaps not try that approach anyway as I’ll have a hard time drilling straight down the shaft of the stud because of the right angle attachment (which, again, is rotating the wrong way for left handed bits!) — best to keep trying the welding?

[wymple]

I think it broke the 2nd time because it's still corroded tight. There are some chemicals that work fairly well to help this out. I am a gambler so I generally push the limit on heat application as that's where I get the best results.

[posplayr]

Thanks, will try as you both suggest. Bought some left handed drill bits, but this particular stud is under the bike frame so a drill can’t be positioned properly since the frame is in the way. I have a Dremel tool with a right angle attachment, and was going to try the left handed bits with that until realizing the tool has no reverse setting, so the bits wouldn’t be rotating in the right direction. Let me know please of any words of wisdom, thought best to perhaps not try that approach anyway as I’ll have a hard time drilling straight down the shaft of the stud because of the right angle attachment (which, again, is rotating the wrong way for left handed bits!) — best to keep trying the welding?

I don't know why but the electrical current of (for example a cheap wire feed) welder seems to loosen corrosion between studs/bolts and the aluminum blocks. Welding on a nut, that you can work back and forth seems to work very well..