So it's been many years since I posted here, I haven't had many problems with my 1993 CB400 however, got home today and noticed the engine temp gauge was looking a little hot. Left the bike running on the drive for 5 mins and it got hotter, and the fan did not kick in. Got to just below the red and still no cooling fan. So I figure the sensor for the fan is not working however when I checked the coolant level it was fine but the coolant was luke warm, the rest of the radiator, pipes and bike were burning hot, could it bee that the coolant isn't being pumped around the radiator, if so where is the pump. Could this be an easy fix (my mechanical skills are oil change, break pads change and clean, minor repairs)??

This is the coolant pump:







Also check your thermostat.The thermostat is under the fuel tank,just above the radiator.There is one or two (i dont remember)wire connectors there.Clean the connectors and check if the wires are in place.

Also the thermofan uses the radiator and switch that's mounted on there as its ground, so make sure there is a good connection for the earth there as well.

Make sure you thermostat has not failed and is still opening, it can cause this as well. If need be you can take it out and run the bike without it to keep you running for a few days while you await parts.

sounds like a water pump failure. You can remove it and inspect it to see if it has failed or corroded. Remember to drain the water before taking it out (obvious i know) and also the oil (not so obvious) or you will get a nice puddle of mixed oil and water and then cannot re-use either.

If you do replace it, I would suggest that you replace also the o'rings, (you'll notice they'll have a squarish cross-section from age instead of round), coolant and oil.

Hope that helps,
Chris