Cooling Issue / Second Fan Mod?

I agree with cap, without proper seal, pressure will not build up in cooling system. Water will not boil as soon under pressure. That's why you never take the cap off when hot, as soon as pressure drops, water boils and spews out.

I have installed manual switch and relay to turn fan on. I really don't think it makes a bit of difference which way fan blows. Riding around town at 30-35 mph, temps rise. Extended traffic lights in our area make it worse. I manually turn it on as I see it get over 190. I rode all day today, mostly above 40 and temp stayed at 175-180, until I came to a light!

 

I'm working on 3 VF1000F bikes here.
I've had a few Over Heating problems, and here's an option that hasn't been covered.

I bought a spare Engine once, from a bike that was crashed, but the motor and electronics were OK.
The motor sat around for years, then I decided to swap it in.
I immediately had Over Heating issues,,.. went nuts trying to figure out what it was, Cap?, Thermostat?,,..
Eventually I removed both Radiators and flushed them, but water flow through was Low?
Closer inspection found this;


There was Rust inside the motor/metal piping.
The Rust flaked loose and plugged up the IN side of the Upper Rad.:grey:
There was also some Rust Flakes stuck in the IN side of the Lower Rad.:grey:
That motor had sat around, and rusted inside, where I couldn't see it.
Also, the Rad Fluid does degrade with usage AND Age.
Maybe the Previous Owner used Straight Water or a Low Glycol ratio.
Change the Rad Fluid Every 2 Years!, 3 years tops, No Matter What.
Use 50/50 mix.

I have ordered a plastic Aquarium Pump, cheap ($8), and will be building a Flush System.
With hoses, elbows, valves, pump,,.. I'll make small hosing loops so I can run Acid (CLR) through various parts.
On my Running Bike, I know the Rads are now good, but the motor/piping is probably Corroded inside.
So I'll Make a Loop of hoses that circulate the Motor Only (not the rads, or water pump, they are fine).
I'll run the CLR (or ZEP equivalent) through the Motor only, and I can run the Flush in reverse too.
I'll run the Flush through the plugged Rads in reverse too, to clear out the Rust Flakes jammed in there.
Of course I'll perform garden hose flush after done.
When I did the CLR flush through the good rads, I did get more flow after.
I found there was still "Cauliflower Growth" inside the rad at the cross tube ends,,.. wouldn't Acid Dissolve?
So I put a bunch of metal Bearing Balls (1/2" dia) in the end Plenum and shook it around, to bust up the Cauliflower.
It worked.
I now know I have a good set of rads that don't leak.
I've considered sending the rads out to a Rad Shop, but I have a lot to do and I'm finding it harder today
to find people who can actually Do Their Job.

I also have a Rad Fan Switch on the dash.
If I know I'm gonna be stuck in traffic, I turn the switch ON, Before it heats up.
Its a Push-On, Push-Off switch, since its easier to operate with Gloves on.
The Switch also has a Light inside it, so I can tell if its ON or not.
Also, this switch must be In Parallel with the Fan Thermistor, NOT InLine with it.

You may not have this problem, or maybe some Crud has blocked one or more rads.
You must remove the rads and check them.
Installing a Rad Switch may Void your Warranty.

Your bike is not 30 years old,,.. but,,.. if you're very lucky, some day, it might be,,..

 

Great post, I will do same to my 83 750 when I get her back and start working on it.