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Today I took my tuned race bike on a quick 4 mile blast (on a private test track !). When warming the engine up it took ages for temp guage to get to 60 degrees then I set off on the test run where it was running at 80 degrees until the last few hundred metres when it alarmingly went to 100 then 120 degrees !!!! so I immediately turned the engine off and whilst waiting for it to cool i stripped the fairings off but could find no signs of leaks, disconnected hose etc and my catch tank only had a thimble full of water in it. There is no sign of water in the gearbox oil, I then topped the radiator up and it took about half of pint, I then started the bike up and ran it for a good 10 minutes before the temp went from about 30 to 60 degrees where it stayed. After letting it cool down again the radiator took another half pint but there is no sign of where the water is going ? I am running a h***a NSR radiator with no cooling fan, could it possibly be that the radiator was just air locked ?

Incidentally its running on 100% Avgas with NGK platinum '9' plugs.

if your head gasket has failed, then it'll pressurise the water system and blow the water out (or you may have an air lock).

Is there any definitive way of checking head gasket failure ?

After topping up the rad and running it for 8-10 minutes before temp went from 30 degrees to 60 degrees and occasionally blipping the throttle to 10,000 rpm - I would have thought ruled out the head gasket and the cooling didn't pressurize again ???

failed head gaskettt doesn't always mean the water is presurised. it can also happen that the engine consumes the water.

I would have thought the exhausts would be kicking out plumes of white smoke if the head gasket had gone ? and mine isn't. Could it possibly be the radiator cap is the wrong pressure rating ? HELP PLEASE !!!!!!

If you're certain you're losing coolant then you trace to find out where.

Gearbox. External leaks. Internal leaks. Passing by through the pressure cap.

If it's not in the gearbox, not leaking on the floor, not passing the pressure cap (it would be in the expansion bottle if it was) then likely it's getting into the cylinder somewhere (base or head gasket).

Sounds more likely you had an air lock. If the head gasket had gone it would start by pressurising the rad with a bit of a leak out of the rad overflow pipe, until it started ingesting water. If it drank 1 pint of fluid that sounds like an air lock. Are you running just water as per race regs. I put proper antifreeze in to coat all the internal pipe work and water pump, get it up to temp, drain it all off to get any crap out, then refill with water. Bleed the pump, squeeze the hoses, and try again. Pour a pint of water on the floor. It's difficult to not see that much fluid if it is leaking out, or boil a pint of water in a pan for 10 mins and see how much steam you produce. (I'm a plumber and just a small amount of water scares people to death when it's spilt)

IMO, if you have a thermostat, once that has opened ,it's allowed what water you had to flow, where as when it was shut, it didn't.

Just my 2 pence worth

I wouldn't be surprised if your head is warped after temps of 120 degrees Paul. 60 degrees is border line too hot on a race bike, you're losing power much over that.

My bike ran around 56 degrees constantly in Jerez and it was about 24 degrees ambient air temp there. I have spent about £600 on the cooling for my bike though, so you would expect it to do its job, if you're chucking that kind of money at it.

Call me if you want to discuss it further.

the impelar seal sometimes leaks and water gets into the gear oil.
I found the standard gauge a bit unreliable, and bought a generic one (same size) which responds much quicker. I tested it against a thermometer and the graduations seemed about right.
for racing though, as Ben has said, a bigger rad is always a good move for reliability and power

Those NSR rads are a good off the shelf upgrade, much better than the RGV or anything else I've seen.

Just had bike running for a full 20 mins in the garden on paddock stand, regularly blipping the throttle to 10,000 rpm, Scitsu temp gauge never went over 45 degrees. No sign of water leaks, radiator kept its water level, all seems fine, now running with 35:1 Fuel/oil ratio. Of course the acid test is riding it but its a bit difficult with a non road legal race bike !

cooling and head sounds fine Paul, put it down to an air lock somewhere.