So here we go!
I'll be using these extractors:
Been soaking this sucker in Kroil every time I've gone downstairs for the past few days. I drilled the bolt all the way through at 1/8 and then again at 9/64. Had my buddy heat up the case with a torch, then tapped in the extractor and gave it a twist.
No go. I could feel the extractor slipping inside the bolt. Tapped it again with a hammer to better seat it, and my buddy gave it a twist. The vice grips he was using slipped on the extractor and made a loud "SNAP!"... I thought that it had broken off inside, but luckily it was just the slip and we were able to wiggle it back out. Here's how it looked:
I kept slowly drilling, stepping up to 5/32, heated the case, tapped in the extractor, twist... nothing.
Up to 11/64.. at this point, the first parts of the threads are starting to pull loose. I grabbed it with some needle-nose pliers and pulled it out. Reinsert the extractor, twist, nothing.
Finally, I drill out at 3/16, which is about is big in diameter as the bolt itself. Since my camber is a bit off, I'm not drilling exactly through the center of the bolt, but catching some of the "upper left" - 11 o'clock-ish - of the bolt's threads and, as the bit exits the back side, into the aluminum case. Not much, just a bit. Here's how it looked from the front:
At this point I'm ready to give up and haul the whole bike over to a guy who can properly fix it. While I'm opening another beer, my buddy looks around at the backside of the bolt and, seeing that there is hardly any metal of the bolt left, and that the backside is not corroded, uses a punch to "bend in" the remaining parts of the exposed threads.
Well, I guess that tapping was enough to dislodge the rest of the threads, and, well, here ya go:
The remaining threads:
When I originally broke this off, I had a hard time getting the shank out of the hole in the cover - presumably because when it broke, the torque caused the end to flare. The same must have been true with the threads that were inside the hole - they flared, lodging them up into the threads in the case and thus would not come out. You can see how it's not corroded at all.. It must have just been the buggered first few threads that were holding it in there.
TL;DR: I broke a bolt, then took my time and some heat and penetrant and was able to finally extract the broken bit.
I'm borrowing a thread restore kit this weekend and we'll see if the remaining threads are still usable.
