1985 Honda shadow whose brakes lock up after a short while cleaned the whole brake system out a refilled it with fluid and bled out all the air bubbles Why are the brakes still freezing?

It sounds like your calipers might be shot - rebuilding might work, replacing will definitely work. Try this article it can guide you through the rebuild process for you calipers http://www.ronincycleparts.com/category/howto/harley/chroming-motorcycle-brake-components/ it is generally a bad seal or a bit of dirt or rust getting caught up in the piston. I would also suggest rebuilding the brake reservoir assembly as this has a piston and spring assembly that pushes the brake fluid into the calipers causing the piston the deploy. If you still have the original factory brake lines and they are not routed correctly they may be pinched during a turn for example and cuasing pressure on the line causing the brake to activate.