Motorcycle Repair: GPZ600R over heating, radiator fan, apear

Question
I have a 1987 GPZ600R that over heated on a ride. I have flushed the system, rinsed with distilled water. I have checked the water pump, and tested the thermostat. Both apear to be working fine. It is still over heating? I have noticed a slight ticking from the engine that aparenty could be a ticking valve. Asuming that it is, could this be what is causing my over heating problems? I have considered that it may be the radiator fan. It only apears to kick on when the key is turned off, Should it kick in when riding at a certain temprature? Im not prepared to rebuild the top end of the engine if that is required. For this bike, that other wise is in great condition, would it be worth paying some one to do it?


Answer
Hi Kevin,

Q:  "...I have flushed the system, rinsed with distilled water. I have checked the water pump, and tested the thermostat. Both apear to be working fine. It is still over heating? I have noticed a slight ticking from the engine that aparenty could be a ticking valve. Asuming that it is, could this be what is causing my over heating problems?

A:  Not likely


Q:  "...I have considered that it may be the radiator fan. It only apears to kick on when the key is turned off, Should it kick in when riding at a certain temprature?

A:  Yes. The cooling fan should power on and off with the set temperatures of the thermal sensor or fan switch. The fan may come on with the ignition key off. This is normal.


Q:  "...Im not prepared to rebuild the top end of the engine if that is required. For this bike, that other wise is in great condition, would it be worth paying some one to do it?

A:  I encourage home repairs and maintenance. Some repairs are best left to the techs. I think you can handle this problem yourself with the necessary tools to do the task properly.

Cooling systems are designed to be air free. Unless you purged the cooling system with a special tool designed for this purpose, there's air trapped in the system and causing the overheating.

Buy, rent, or borrow a tool such as a AirEvac tool by MityVac to purge the air from the system. You can see this tool on line by performing an inernet search of it's name.

Use this tool anytime you open the cooling system to air with the exception of removing the radiator cap.

You could have a shop do this for you. Be sure to ask if they use such a tool when servicing the cooling sytem. If not, go elsewhere.

Respectfully,
Mark Shively




Cooling System/Engine Overheating

Primary cause:
Air in cooling system

Firing incorrect:
Spark plug dirty, broken, or maladjusted
Spark plug incorrect
IC ignitor trouble

Fuel/air mixture incorrect:
Main jet clogged or wrong size
Fuel level in carburetor float chamber too low
Carburetor holder loose
Air cleaner clogged, poorly sealed, or missing
Surge tank duct poorly sealed

Compression high:
Carbon built up in combustion chamber

Engine load faulty:
Clutch slipping
Engine oil level too high
Engine oil viscosity too high
Drive train trouble
Final gear case oil viscosity too high
Brake dragging

Lubrication inadequate:
Engine oil level too low
Engine oil poor quality or incorrect

Gauge incorrect:
Water temperature gauge broken
Water temperature sensor broken

Coolant incorrect:
Coolant level too low
Coolant deteriorated

Cooling system component incorrect:
Radiator clogged
Thermostat trouble
Radiator cap trouble
Thermostatic fan switch trouble
Fan relay trouble
Fan motor broken
Fan blade damage
Water pump not turning
Water pump impeller damaged