VF500 temp gauge question

Hi, I went for a ride and had to go through downtown (stop start). I noticed my temp gauge moved closer to the H,(3/4) but never actually reached the H. The fan was kicking in as it was supposed to.

Just wanted to know if this is common or should the needle remain in the middle and I should be concerned.

I have a 1985 VF500 Interceptor (30,000 miles on the clock). Just recently passed a stringent Out of Province inspection.

Thanks

 

My 83 750 does the same thing. I have gotten in the habit of letting fan run for awhile after stopping, then restarting for a minute get cooler water back in the engine. (getting rid of heat soak).

 

Thanks, good to know. So it sounds like this is a common issue/normal issue.

I feel more relaxed now.

 

If it gets worse, invest in a new radiator cap, got to keep system pressurized.

 

What you had there was normal for most water-cooled bikes, not just the VF or VFR.

 

Since the bike is 31 years old you might want to check the temperature sensor. Your VF500's temperature sensor is probably (almost certainly) a "through body" grounding type. When the temperature of the coolant goes up the temperature sensor gets hot and this is what makes it "flow" more current to ground which will cause the temp gauge on the instrument cluster to indicate higher temperature.

The temperature sensor depends on a good path-to-ground for proper operation. The way this sensor works if there isn't a good path-to-ground then the gauge on the instrument cluster will never be able to go "full scale" hot. Some manufacturers depend on the metal in the bolts that hold the thermostat housing to the bikes frame, while other manufacturers take extra care and include a grounding wire from the thermostat housing into the bikes ground-path wiring in the wiring harness.

 

Thank you for you input and information, as a beginner I am learning everyday. Appreciate the replies. I will keep you all updated.

 

The cooling control system on a water-cooled bike consists of the thermostat and the fan switch, plus the radiator cap.

The thermostat is a mechanical device that stays in a closed position until exposed to coolant at a normal operating temperature. In action, it holds the coolant in a circuit through the pump, water-jackets and back to the pump, bypassing the radiator, until the coolant reaches "normal operating temperature", usually around 80C. Once that temperature is reached the thermostat starts to open and allows the coolant to start flowing through the radiator. The thermostat's function is to allow the bike to reach a steady operating temperaure in the shortest time after start up, and to maintain that temperature even when the radiator cooling effect is high. Typically, 80C will be about 1/4 on the temperature gauge. Thermostats do die in older bikes, usually they stick open so heat up is slow and the engine may run at below the target temperature.

The fan switch is an electrical temperature switch on the radiator and is independent of the thermostat or gauge. This should switch the fan on at a coolant temperature of around 100C, which is usually the 1/2 mark on the temperature gauge, and off when the temperature falls below that. It is normal on a water-cooled bike for the fan to start switching on/off once you are in stop-start conditions, as there s little or no airflow through the radiator. If the fan fails to run, it can be caused by debris jamming the fan blade which will cause the fuse to fail, or the switch itself. Fan motors are energised with 12v at all times, the switch simply completes the ground.

The "H" mark on the gauge corresponds to around 120C, and that is the redline for temperatures. Honda advise that you should not operate the bike at temperatures above this.

The radiator cap is designed to allow the cooling system to pressurise as it heats and the liquid expands. Above a set pressure (usually around 16-20psi) the cap will open slightly to allow excess pressure to escape to the expansion tank. As the system pressure increases, the boiling point of the coolant also increases so the coolant can do it's job without localised boiling. If the radiator cap fails to seal and hold pressure, cooling efficiency is reduced. As the coolant cools when the bike is shut off it contracts, and will draw coolant back in from the expansion tank.