Drained radiator = sooty fluid

Just drained the radiator and coolant for the first time owning this bike. No problems running the bike, but noticed that the fluid is dark dark brown w/ very fine soot settling from it. Is this normal???? Previous owner said all maintenance run at norm intervals and bike is an '08 w/ ~10.5K miles

The fluid in overflow tank was still bright pink...

sounds like casting sand left over from moulding the heads, a few people have had proplems with the same thing including myself.
recommend flushing a few times before refilling with anti freeze/water.
i,m also doing water pump seal a precaution

I'm guessing someone thought they'd top up or changed the coolant to a different product (incompatible) with what was left in the system. GM dexcool if famous for turning brown like you mention and happens to have a pink/orange color...? Ethylene and Propylene products do not mix well.

I did find a decent amount of casting sand in my reservoir but not much when i drained it? But shouldnt do much to add a brown color.

refill with water and run it, drain again then refill with fresh coolant (correct product!) and distilled water (if required) at the correct ratio.

I use a ramp to get the front end high (front tyre only)upon air burping.