Motorcycle Repair: bike overheating, kawasaki 454 ltd, coolant pump

Question
Hi Mark
I have a 1987 Kawasaki 454 LTD and it overheats after you run it awhile (more so in stop & go traffic). It gets up near the red line and then pushes out radiator fluid which I have to constantly refill the resevour back up to full. My question is should I start with a new thermostat?(I already ordered it) or do you have any other suggestions. I have heard the fan kick on but like today when I road for awhile it got up near the red line so I parked it and shut it off and I never heard the fan come on. Any helpfull advice would be appreciated because I truly love riding this bike.
sopranotrek@comcast.net

Answer
Hi Gino,

Overheating may be the result of one or more of the following:

Defective thermostat
Defective thermo-sensor
Defective fan switch
Defective fan motor
Defective wiring/connectors
Defective coolant pump
Improper coolant mixture ratio
Air in the cooling system
Other

The most common cause of overheating is air in the system. Cooling systems are designed to be air-free.

If the system is opened to the atmosphere other than removing the radiator or reservoir caps for inspection, air has entered the system.

Air MUST be purged from the system. A purging tool is used for this procedure. I use and recommend a purge tool manufactured by MityVac called the AirEvac tool. It costs about $100 depending upon the retailer.

I'll send some tech files to your email to assist you with diagnosis and repairs.

Respectfully,
Mark Shively