So little known fact online is that I love bionicle. Not just the new ones, but the 2001-2010 sets too. Unfortunately, the older ball cups have a tendency to break. This has prompted me to find a solution, and although it's not the most amazing, I think I did a pretty good job...
Step 1: Suppliez
Yes, that "z" in supplies was intentional. Anyways, you are going to need a file or some sort of surface to sand on, a bionicle joint you wish to repair, a hero factory friction adder (if you have none, buy them in bulk on lego.com), some epoxy putty (I used jb water weld), and possibly a dremel. Seriously, if you want to reinforce more than one set, you are going to need one if you don't want to spend your weekend sanding down lego parts (seriously, lego does NOT want their parts sanded by any means, so just use a dremel if you have one.). Just don't forget to hold the part with a pliers or some tool so that you don't sand your finger off.
Step 2: Sanding
This is pretty simple. Just sand the pieces down to a straight point until the fit together well enough. By the way, ignore the white on the other end of the joint, that was another try at reinforcing joints.
Step 3: Joining the Joints
For this, you need your epoxy. Don't forget, the reason epoxy hardens is because it was mixed with the other half of the mixture, so mix it thoroughly so it's sturdy when it dries. Then attach the two pieces together, then let it cure for 24 hours before handling the piece.
Step 4: Conclusion
So this is the joint when finished. As you can see, the cup is slightly further forward on mine, however I probably could had sanded more. Also, this comparison is legit, because they have been joined by a red no.2 axle. By the way, I know this is a very low quality and frankly quite rushed 'ible, so sorry for that, however I should be making a new version soon. Good luck, and PUMA OUT!