Last night swapped the antifreeze out of my 04 CBR1000 for the first time since i bought it in 2012. The bike has about 9,000 miles on it. The owner before me swapped out in 2007. In the first few seconds of flow out of the drain plug in the coolant pump, the antifreeze was a dark brown; once the flow got started, it was the typical bright green. Also, when draining the reservoir the antifreeze was bright green until the last maybe inch, which was then a milky white/brown. Could this been a blown head gasket? If so, how immediately should I fix it?