Thanks Derek,
I think you're right about the likely culprit being the relay, but first thing to do is supply a seperate 12V to the fan as you say.
The bike displays in farenheit. The fan should (and used to) come on at 200.
This was a rare occurance until you have a heatwave and only then when pratting around at slow speeds in town traffic. However, I've had a reading of up to 220 degrees on 3 occasions last week alone.
If the fan works OK, and the relay is fine, then frankly I'm out of ideas.
Thanks again for the reply.
Mike