Hi all, looking for some advice.

The fan on my radiator is not kicking in at all, let the temp of the bike get to 120 before switching off but the fan did not come on at all. i walked away and let it cool down, then i went removed the ground from the thermoswitch on the rad and connected this to the frame and bang, the fan came on full spin, brilliant so you would think the switch is the problem. i tested the grounding of the fan several times on several points to be sure it wasn't a short and each time it worked a treat.

Bought a replacement switch, fitted said switch and warmed the bike up to 110, no fan, nothing. tearing my fair out. turned it off and disconnected the switch and tested the ground wire on the same ground points as yesterday and no fan at all, kept testing and the fan did kick in once with a real weak spin. but 90% of my grounds failed to get a spin. so at this point thinking it must be a live feed at fault.

Walked away from the bike again and went back a few minutes later when it had cooled to around 60 did EXACTLY the same thing touched the ground to exactly the same ground point and the fan spins up full pelt tested it another 10 times and again twice this morning and every single time, the fan spins.

WTF? does anyone have any ideas? all i can think of is ironically enough the cooling fan will not spin up when it is hot! when it is cooler it runs like a jet engine but when its hot it wont spin at all...

 

You didnt say where you're from so the temps, are they F or C ? So with that.......I believe the fan shouldnt kick on until somewhere above 200 degrees F. My 08 cbr 1000rr U.S. spec fans dont come on until 205 ish F for the first one. The second fan dont come on if the first fan can lower the temp, if not 225 F and the second one comes on also.

 

UK so everything in Celsius, the 01 F4 only has the one fan bolted to the rad.

 

Check the ground wire from the fan shroud to the frame. The radiator mounts on rubber, so the additional ground to the frame is needed.

 

Grounds are all good cause everything works perfectly, when the engine is cooler, as soon as it gets above 84 celsius on the dash thermometer the fan gives up.

Im convinced its heat related, i have insulation taped the wires from the connector box above the upper radiator hose and the ones that enter the fan itself and got to 90 celsius until the fan quit.

 

Sounds like the fan motor is heat sinking and cutting out. I'd replace the fan.