Suzuki 2 Strokes

What should one expect from the fan on these bikes? Whilst reinstalling the carbs after a rebuild, I noticed a disconnected wire - so I dutifully plugged it back into its socket . When I next turned the key on I heard the fan spinning away and realised that it hadn't been going before. I thought they only cut in at certain temperatures or something. Should it be coming on as soon as the key is turned on or what do they usually do?

Thanks

Mike the fan only comes on when the sensor in the top water pipe closes the circuit due to a predetermined amount of heat from the coolant. So it looks like you have a faulty sensor there if you connect the wire and it runs. However, pull the tank and verify its wired correctly underneath.