Congratulations, you just performed an unintended maintenance item.
Coolant really should be flushed and changed out every couple of years.
You should drain and clean out the coolant reservoir while you're at it. You can gain access to it under the false tank lid. Sludge tends to collect at the bottom of it, I use a hose connected to a shop vac to suck that out - then I'll pour water in, slosh it around, and suck that out, until it's all clean.
Have a look at
How to flush your cooling system for some details.
You're going to need to get access to the radiator cap, which means you have to remove the false tank. All told, you'll need 3 quarts of coolant - you can use any automotive non-silicate (important!!) coolant, but I use Honda HP coolant on my bikes, and have for years with excellent results.
Once you've filled the radiator, run the bike for 3-4 minutes with the cap off and top up the radiator as the level drops (this is required to "burp" the air out of the system). Then replace the cap, fill the reservoir to the "full" line and you're done.
