TOPIC:

This may have been mentioned, but I remembered the 1300 has a temperature switch that bypasses the radiator when the bike is cold (to help it hit operating temperature faster). If this switch stuck shut, your coolant may be bypassing the radiator completely. If I remember correctly you can access this pretty easily (pull radiator, pop down the coolant bypass tube, remove the cover, then the switch), so it may be worth a look.

Lucien,

You got me really intrigued here with that info ?

I am not aware of any such temperature control switch on any 1300 (carb model), especially where you mention its located.

The only switches in the cooling system I know of are the Fan Switch at the top of the motor on the inlet pipe housing and the Temp Sender Switch also at the top of the motor at the front.

Are you referring to the THERMOSTAT unit as that sits in a small casing at the top of the bypass pipe in the middle of the motor at the front.

Pete F
UK

Im with Pete on this one as well.
there are no switches as such
when the stat opens the base of it closes of the bypass pipe putting water through the rad.
if the stat doesnt open then as Lucien says, you would be bypassing the rad and not cooling the water.

I think he is referring to the thermostat "mechanical switch" or valve?

Yeah, that thing! (Thermostat sounds right) It's been a little while since I've been through my engine, so I forget the exact names for things.