Cooling system

Trying to sort my cooling system before Summer.
Last year on very hot days, in traffic, with the fan switched on manually I was overheating.
Once out of the traffic and on open roads no problem.
Took my thermostat out today and dunked it in a jar of boiling water and it opened, so that seems Ok.
Put it all back together and ran engine almost to red on gauge and Fan did not cut in ( I purposely didn't switch it on Manually so as to see if it worked automatically) The bike blew water out of the little expansion tank, then I stopped the engine and could hear the water boiling. I have a spare thermostatic Rad switch witch I will try tomorrow.
Thinking about a new thermostat, but don't want to spend unnecessary money.
My questions are: where on the temp gauge is the fan supposed to cut in?
How far should the thermostat open?
Shall I take thermostat out altogether?

Would appreciate comments, thanks.

Have you got a seperate switch for your fan then ?? Not rely on thermostatic fan switch to kick in ??
I have a spare thermostatic fan switch and rad thermostat if you should need one.

You need a replacement thermoswitch, which is fitted to the rad. The thermo switch is a heat switched ground.

There are 3 separate parts to the cooling system, the thermoswitch (which turns on the fan using a switched ground based on restanance), the thermostat (which restricts the coolant flow to keep the engine running at an optimal temp), the thermo sensor ( this is also a resistance based heat which gives the the temp shown on your temp gauge on the clocks) .

There's really one more part to the cooling system which might be worth considering.   Could be wrong here but the water shouldn't be coming out of the expansion tank........ if it's overheating, it should come out of a small "rubber" pipe underneath the bike (comes from by the radiator cap)..... it certainly does on my ntv650 so presume they're the same. It suggests to me that the radiator cap is faulty and not sealing properly ..... this would allow the water to "boil" at a lower temperature and affect the cooling system significantly.  The fan switch might be faulty as well  of course and this can be tested with hot water and a multi meter.

Thank Guys. I tried a second rad cap, made no difference, going to change the rad thermo switch today.
Will keep you all posted.

Does seem like the bike's overheating though in traffic.. even when you've manually switched the fan on.  Might be worth flushing the radiator through using a hose....reverse direction from the normal flow... haven't used the stuff but seem to remember there's something you can buy which will help clear any junk in the rad. Are the "fins" in the rad blocked with general "crud"? On my NTV forum, have heard of the pump being badly corroded so the impellers aren't functioning well..... this might be a last resort! 

Regarding the thermoswitch...... only going on my ntv here (its my son that has the cb500 in case you wonder why I'm here!!)
It might be worth checking the actual connections/wire to the therm switch before replacing it. With the ignition on, Take the wire that goes to the switch and press it
against the engine.... the fan should come on..... if it doesn't, there's a fault in the wiring to the switch.  If it does, then press it against the actual radiator where there's exposed metal..... the surround of the thermoswitch works well. If the fan  now doesn't come on..... there's a fault with the earth wire connectoin  that goes onto the back of radiator..... this can become badly corroded and cease to function.  I'm only going on an NTV650 here so the cb500 might be different.
If fans still not working, then try the switch... they're very expensive so I'd try the first "tests" before you  splash out.

Going to check all electrics today and make sure Fan has a good connection to back of rad.
Had thought of water pump impeller, may have a look at that today as well, I have a spare engine which I can take the water pump off, will also take Rad off, have a spare one of those as well.
Do you sometimes wish you hadn't started something? Still it has to be sorted.
I have had 2 Deauville's nice bike's but a bit on the heavy side for me, I find the CB very manageable.
Happy days. (Bootiful)

Removed Radiator and Fan fell off, brackets rusted through. Have ordered new Rad and Fan off eBay £140.00 Fed up codging and bodging. (wife will go ballistic)
Removed and stripped Water Pump, Impeller all Ok, refitted, (had to take left crash bar off to draw pump out)
Tried to check Thermo switch in Boiling water with Multi Meter did not get a continuity, so assuming it is Fu***d.
1445hrs now have pushed bike back in shed, have had enough for today. 

@davecb5002 wrote:Have you got a seperate switch for your fan then ?? Not rely on thermostatic fan switch to kick in ??
I have a spare thermostatic fan switch and rad thermostat if you should need one.

Have PM'd you Dave about Thermo fan Switch.

See pics of fan

That doesn't look like an OEM rad so probably changing it was the better choice

All sorted, new rad and fan, thermos switch in rad, fan cuts in when the temp needle is half way, so happy with that. Had a few minor water leak issues from around the thermostat, but a new O ring on the plastic filler neck bit and nipped up the hoses put it right.
Ran it to working temp took tank back off topped up coolant and Bob's your uncle.
Daft isn't it that you have to take the tank off to top up.
Waiting for weather to warm up now.

Fair Weather, hello, shurely you only need to fill the rad when you do any work on it and you refill it, topping up is done via the plastic expansion bottle as in a car?
Certainly I won't be arsed to take the tank off every time!
Dave

@motofan wrote:Fair Weather, hello, shurely you only need to fill the rad when you do any work on it and you refill it, topping up is done via the plastic expansion bottle as in a car?
Certainly I won't be arsed to take the tank off every time!
Dave

Have had so many problems with cooling, wanted to make sure there wasn't an air lock, will trust expansion tank now I know it's full, but will be keeping an eye on it.

Aha, you have my entire understanding, things like that irk me as well.

If there us a leak then air will get in the system so the overflow tank will not siphon into the main system. I found this out almost too late

Good point, I make a habit of squeezing my pipe(radiator I mean, OOER) when the motor's hot and verifying that it's turgid! If it's soft then it's not holding pressure ie. leaking somewhere.