I tried to remove the battery so I could add distilled water and the positive battery screw won't come off. It appears that the nut that holds the screw is stuck to the screw and simply rotates in whichever direction I turn the screw. Now I can't tighten or remove the positive terminal. Any ideas on how to remove?
Well, as long as you remembered to remove the negative cable first, the bike should be safe to work on. You don't want the frame connected to ground (the negative side of the battery) while you work on it. ALWAYS disconnect the negative first, and install it last. That way, if you're touching something connected to the positive side, and then somehow short something to the frame, you won't fry the electronics.
You should be able to get the nut off with needle-nose pliers, or a small open-end wrench in the correct size (probably six or eight millimeters). Whatever you do, don't let anyone talk you into cutting the battery cable. Be resourceful; if you can, jam a flat-blade screwdriver in against the side of the nut to hold it while you turn the screw; that might work. You have to think like a mechanic in order to solve these annoying little mechanical problems, and each time you solve one, you'll be better prepared for the NEXT time you hit a snag, especially the BIG ones.
If those methods don't work, try something else. Put a coin or a washer behind the nut, wedge it with a flat-blade screwdriver, and THEN try to turn the screw. Just take your time, and if all else fails, check back here for more solutions from other people, or call a local shop and ask them for some advice (HA!), or take the bike to a shop and ask the mechanic to show you what to do.
Once you get it disconnected, you might want to replace the screw and nut with a nut and bolt, which will work better. You can get a wrench on a bolt, which gives you more torque when you need it; you have a lot fewer options when you're using a screw.
Good luck; let us know how this turns out.
Thanks. I will try a few things this evening after work.