Motorcycle Repair: 2005 yamaha yfz450, thermo sensor, engine coolant

Question
I have a 2005 yamaha yfz 450 and my header pipe will start glowing red after it is running for about 2 to 3min, my fan is not coming on but i can hook a hot wire to it and it comes on but my heat switches in the radiator comes on do you no what the problem is.  

Answer
Hi Matt,

I suspect the choke (starter plunger) is applied too long during starting or is not completely off and is remaining open.

When the air-fuel mixtures are excessively rich by the choke system and left on too long, the pipe will glow as described.

The temperature of the pipe and cylinder head may not be the same as the engine coolant. Coolant temperature may need to raise before the thermostat, fan switch, and thermo-sensor turns on the fan.


Respectfully,
Mark Shively