I don't trust the jb weld method at all. If mine would ever break i'd just replace the case. My cousin jb welded the same thing on his suzuki quadracer, and it held up for about 5 months with no leaks or anything. Then one day riding at paragon, the junk broke loose and his entire engine was destroyed because he didn't know he had a problem until halfway through the mud pit his clutch started slipping because all his oil had been displaced by muddy water.
If you can't get it to stick at all, it sounds like first you need to properly prepare the surfaces. You can't just jb weld 2 oily broken pieces together. You have to grind them down good first to get rid of the jagged edges caused by the break, and make damn sure you have absolutely no oil residue on either pieces. Then lay the bike over on the right side (don't do this if you have a lot of gas in your tank, or it'll leak through the cap breather). When you lay it on the side, you won't have to hold it for 10 minutes until the compound starts setting up. Wait at least 24 hours before moving it to make sure it's set completely. Don't do it on a humid or rainy day, or a real cold day either, that can keep the compound from curing properly.
If it were me, i'd grind off the rest of the remaining chain "guard" on the broken piece, so that you don't have that wing sticking out, because you don't want to catch that thing on your foot and bust it off again.
And the final tip I can give you, don't use JB quik. It doesn't hold up as well as the original, especially when it's on an engine and it's frequently being heated up and cooled back down.
