I was in the process of reassembly after powder and, following the manual, iput the rear lower rocker box on, followed by the rocker frame and then went to the breather assembly.
I guess I didn't follow good engine tear down/rebiild practices and when I went to torque the breather bolt on the spark plug side it seemed normal but suddenly there was a "ping" and I thought I broke the bolt! Removed the bolt and it was ok so I got to looking around and I see a bit of oil on the spark plug area of the cylinder fin and a little piece of metal sitting there. I realized I had hydro locked some oil in the bolt hole and it popped to base of the head casting at the bottom of the threads. So now I look for suggestions on what is my next move.
Motor has 10,000 miles on it. The area that broke off only seems to be for that bolt and not a oil route/passage.
My thoughts run from the conservative (just replace the head or have it welded) to crazy (JB Weld in the base of the casting making sure it gets up into the bottom of the threads, shorten the bolt just a bit and roll on!)
Let the laughter begin :-/

 

On the bright side it's cold as *****, with snow and I have time. It's a shame cause she was lookin soo good!

 

I would probably take it to a welder and let him fill it in and then have it cleaned up for a good mating surface. Bring the piece with you but he probably won't want to put it back in but just fill it....

 

If the pop-out piece serves no purpose then i would just ride-on.
Looks more like the termination of a threaded hole.

 

I inspected the area as best I could and it is in the area above the combustion chamber supporting the rockers and rocker boxes. I think I can get away with JB Weld to plug the base of the hole and blue loctite to seal the threads. So this is what I did....
Cleaned the holes out the best I could and chased the threads to clean. Filed the bolt that will go into the damaged area about 1 to 2 mm, just enough to allow me to put JB up into the hole to give it a better chance. Installed the breather assembly with blue loctite being very careful with the torque wrench (a little gunshy at this point)! Taped off the recess behind the spark plug with painters tape to keep the mess off other surfaces. Mixed the original JB and used rubber gloves to finger apply it into the hole and build a support nub (like the original broke off piece) waited until JB cured for a time and then ensured it was up in the hole and shaped the way I wanted. That is a tight space and the gloves came off pretty early in the process as the JB stuck to them like, well, glue ... Not allowing me to effectively mold it. A little trick I learned from my Father when I used to work with him is to spit on your finger and then mold the material not allowing the spit to get into the stuff but just enough to keep it from sticking to your finger.
Today I'll run a compression test (recommended by a forum member) just to be on the safe side in case the injury put a crack into the casting. Don't see how it would affect the rest of the head but I didn't think about checking the threads for oil either when I broke it in the first place! As I said the damage is above the compression chamber.

 

Are you sure you had the right bolt in the right location. not the most familiar with tc's But looking at a diagram it looks as if some bolts are longer than others. Just a possibility that maybe you should check ,

 

Good thought and both sets of rocker cover bolts have two lengths but the rocker frame bolts are all the same and the breather bolts are the same.

 

That certainly looks like the bolt bottomed on that piece and not a hydro lock. Do you work on other bikes? The reason I ask is the early aluminum breather housings used a slightly longer bolt than the late model stamped steel ones do. Just wondering if a bolt could have gotten swapped. As for the fix you really only need to be sure that the threads are sealed and you should have no structural or other problems associated with this.

 

I remember when it happened I went to the original bolts that came off the original breather and they were the same length. Plus the oil blobs that were on the plane of the spark plug fin area. That's why I figured it hydrolocked. I hope you're right about the structure. I went to do a compression test and damn if I could source a 12mm small engine adaptor for my tester! I used the po'mans finger over the spark plug hole which proved nothing but that fact that my finger blew off. Thanks for the thoughts. I tend to agree with you.

And no, I'm just your average do it yourselfer. I work on all my own stuff. Only way to learn is to break it... Fix it and move forward!

 

I thought I replied to this to close the loop and serve up a resolution....?? but here's what happened....

I sprayed brake cleaner down in the hole to clean out any oil residue. I shortened the bolt by around 3mm, put it in without the breather assembly and then put JB Weld into the bottom of the hole where the metal blew out. Let it set up and then put the bike back together over the next month or more. When I installed the breather and bolt during final assembly I made sure to put some extra blue locktite on the threads. I was able to get the adaptor I needed and ran a cold compression test. Rear jug was less than front but all within acceptable limits according to what I have read here and elsewhere.
I now have another 2300 miles on and my fix seems to be holding!

Thanks for the posts and suggestions