I`m disturbed with that as soon as I go below 70 km/h, in 5 mins coolant temp rises quite rapidly to the +100C`s.
Weather temp doesn`t seem to matter.
Fan kicks in at 92.
Above 70 km/h all is normal, coolant temp varies 10-20 degrees depending on ambient temp,
could be 80 a hot day w spirited driving, 60 a damp autumn evening.


Is this normal behaviour of the 907?
What temp do you see in same conditions?
Don`t mind going 70+ but not always practical....

Doesn't sound right to me Gert. My 906 only ever ran hotter whilst stuck in traffic and then it only switched on the fan for a minute at a time .
Hamish

better check your pump

Pump meaning what, fuel?
Or impeller?

Hey Gert!

The impeller. I would check to make sure the thermostat isn't sticking shut or sticky as in opening late. Also, some coolants don't last as long as others. May be time for a good cooling system flush while you are checking everything.

Impeller has no broken wings & sits firm on axle.
Radiator flushed thoroughly.
Rad fins separated thoroughly.
Thermo tested, opens. Fast/correct or slow/sticky, I can`t tell.
Air temp sensor works, will check rest of electrics involved w scan tool this evening.
Air from coolant removed via squeezing hoses & refilling til level is still & no burps occur.

The feeling I get is that coolant isn`t cooling at all, only air when I drive.

How do one setup & test the cooling system properly?
Can any one descibe how a fully functioning thermostat open & flow?

Sensors & TPS tested, all good.

Think I`ll try and lend a thermostat.

the t/stat , when cold allows the coolant to circulate round the engine without passing thru the radiator , as the engine ( and thus the coolant) warms up the stat starts to open allowing coolant to pass thru the radiator . Under normal running the stat allows some coolant to pass thru the radiator and some to just recirculate thru the motor . Ideally the stat will open and close a bit to balance the cooling effect to the heat produced by the motor ( this varies with speed and load ...IE stop / start riding in heavy traffic will require the stat to allow more coolant thru the radiator ... coasting down a hill will require less ) Air flow thru the radiator is reliant on forward motion and when that slows down coolant temp goes up .... stat opens to allow max flow thru radiator , which is now not cooling all that well ( lack of air flow due to low road speed ) and then fan comes on . Im thinking that either your stat is not opening fully or there is some other restriction to coolant flow , like maybe a coolant hose has collapsed inside ... whatever is going on I think the end result is that not enough of the coolant being circulated by the pump is actually making it thru the radiator . I can see that a stat that has been operating in more or less the same position for 20 years would begin to "stick " there . Does the engine take longer that it used to to warm up ?
Pleased its not mine
Hamish

Gert, I think your bike is running on the hotter side of normal (Sweeden has a cool climate) have you tried to remove the thermostat body from the cooling system and run the bike without it to see what happens

Hamish, that was a good and thorough explanation

Seems a plausible explanation, Hamish.
Guess you have enough problemos of your own....
Warmup time is normal.

I'll think l'll try w workin thermo f a start.
Runnin w\o, how to d that?

One simple check is to grab the radiator when the temp comes up to confirm that water is running through the radiator. If the engine is warm, and the radiator isn't, then your thermostat isn't functioning properly, or there is blockage.

Also check that the water level in the overflow bottle is changing from hot to cold. A simple mark on the bottle for the level when its cold, then noting where it is when hot(should be higher). This is a function of your radiator cap, and caps do fail from time to time.

My 98 ST had some odd gel thing happen that blocked the water overflow tube, and had to be flushed out.

Sounds like you looked at all the other things I could think of.

Cheers, Phil

If your thermostat is working, then all three hoses should be at the same temperature when you touch them when the engine is hot, and so should the rad be equally hot throughout. The fan should be cutting in and out.

On my bike, when the temp gauge shows excessive heat, the cure is to short two of the pins on the back of the gauge and that resets it. The bike is not overheating, just the gauge is wrong.

If the bike is really overheating, the likely problems are:

Airlock in coolant system
Kink in coolant pipe
Failed water pump
Sludge in radiator
Mixture/timimg way off

Simplest thing to change is the coolant. Too much coolant and too little water will not cool as well. Wash out the rad and coolant system and refill and bleed. If it still overheats (and your thermostat is working) then the water pump has failed.

If it runs real badly and barely starts, check mixture/timing.

[quote]On my bike, when the temp gauge shows excessive heat, the cure is to short two of the pins on the back of the gauge and that resets it. The bike is not overheating, just the gauge is wrong.[quote]

But my temp gauge & fan correlates.
They have separate sensors and at +90C, gauge shows high temp AND fan kicks in.


Will do the 3 hoses check & reconsider ev timing issues.

Hi Gert.

I was talking to mate of mine about what sort of coolant is best (he's a mechanic. There seems to be all sorts of varieties, pre mixed green, pre mixed red, concentrate green, concentrate red etc. He didn't really have an opinion, but he did say to be careful if there was any chance of the 2 colours (red and green) mixing, as apparently they don't mix very well. Green to green is OK, red to red is OK, but green to red is not good. Not sure what happens if they mix? I will ask next time I see him. I have used the pre mix green on all the changes I have made, different brands, and the temp gauge always sits around the 90degC mark. Its SFH here at the moment, so engine temp is high most of the time, but rarely if at all does the Fan kick in. We don't get much start/stop traffic though.

Not sure about the short out the gauge trick? The temp sender would be a heat dependant resistor in series with the gauge. 12 volts would be attached in there somewhere, so shorting out the gauge may short 12 volts to deck.

Cheers.

Nick.