OK, this just started happening and it's possibly a bit tricky. My bike is streetfightered, meaning no fairing and a single digital instrument which does everything but engine coolant temp. Yes, i'm running without a temp gauge.

My bike has just started running hot. I know it cos I can smell it. Coolant in the radiator looks fine - nice bright green. Oil level is fine and clean. So i'm thinking maybe thermostat is stuck or water pump problem. Both the oil and water radiators are getting hot (although maybe not as hot as I think they should). The radiator fan is not coming on.

Any belt and braces suggestions more than welcome.

I'm thinking I should be able to test the radiator fan itself by just whacking 12 volts on to it?

 

"The radiator fan is not coming on."
This is your problem - motorcycles depend on the fan at low speeds and at idle, it will surely overheat without it. Try running wires directly from the fan to the battery - it may also be the temp sensor - make sure the wires from the fan to it are securely fastened.