I'm no expert but check these links.

http://wiki.answers.com/Q/Why_do_you...to_the_coolant

http://autorepair.about.com/od/autor...antifreeze.htm

Personally I would drop whats in there at the moment and refill with fresh. I would not worry about the car/motorbike senario - coolant is coolant or should I say antifreeze is antifreeze?
Have you a leak in the system???

__________________
Work hard, rock hard, eat hard, sleep hard, grow big an wear glasses if you need em.