That's an oil cooler on the Bandit 6/12.
A fan isn't really needed. If the bike gets too hot, your legs will tell you!
You'll notice the heat if you ever get stuck in stop/go traffic in a traffc jam. If the heat seems excessive, pull off and shut the bike down for a while.
It RARELY happens......but, idling on pavement, in a traffic jam, during the summer, in the south....and you'll notice it!