Noise coming from bike after riding hard
My 2007 650r, after riding hard and turning the engine off, I can hear a "sssssss" noise coming from the bike. I believe it may be something to do with the coolant due to only happening when the bike is quite warm. In addition, the bike had been sitting a long time. I don't know much about it (was bought at auction) but the tires were from 2011. I put new tires on and changed the oil, is there anything else that I should do to it to ensure a safe and reliable ride?
EDIT: I would also at some point like to switch the coolant and brake fluid, are there beginner friendly guides out there for doing so?
Any Help or advice would be greatly appreciated!