Lilredmachine

I would start by draining the carbs. Often you can have a bit of debris in there floating about that will jump into a main jet on heavy throttle opening. That's the easiest thing to do/check. Next would be plug caps, check they aren't arcing out on the inside of the cylinder, however this would generally be a repeatable thing and consistent, it wouldn't do it randomly. It could also be an early sign of a coil failure. If your bike is still on the originals they are now old and right about where they let go age wise...

Edit: on the battery front, I don't think it's related to the running issue, but get a new one quickly if it is duff. A weak battery will cause havoc with the charging system and damage far more expensive components than a cheapish battery will cost to replace.