overheating

yamaha dt lc goes straight into the red within 5 minutes of riding/ticking over, tried various doses of anti freeze-no anti freeze
water pump seems fine took the cap off the radiator and the water was pouring in, felt the bottom hose and water was going through
does'nt seem to be any major damage to the rad, although it is 27 years old
any thoughts would be appreciated, as it's doing my nut in

weot state is the radiator cap in ?

Check the temp switch it might be faulty

Take the thermostat out.

radiator cap is fine, no thermonstat on the mark ones and isn't the temp switch just a brass nut in the top of the cylinder head??

Yep that's the sender take it out and you,l find thee a long brass prong under it about half inch long.
Has it actually boiled over yet while ridding it?

no,after boiling the kawasaki on clutch fryers i've learnt my lesson    
what could go wrong with just a lump of brass???

The temp switch on the ktm for the fan a common thing to break down Geraint beats me how tho! too.

geraint powell wrote:no,after boiling the kawasaki on clutch fryers i've learnt my lesson    
what could go wrong with just a lump of brass???

I have no idea but cant be an expensive part or can it? I,d ride it and see it how hot it gets, Wait till it go,s into the red and just feel the rad and cap you should soon be able to tell if its red hot.

It works on resistance and sends a signal to the temp gauge
i change loads on cars there cheep as chips for most cars
pull it out ond put it in hot water and see what happens to the temp gauge if the water is 80 degrees the needle is in the red the switch is fooked
you can test them with a mulit meter at diffrent temps but you need to know the correct resistance for the switch