I'm pretty sure the switch is on the stat housing under the airbox.

Thanks yes I can see it I can't see how to get a tool on it?

Air box off I think!

Tjanks I think a fee oyther things also but thanks for reply!

just typed out a big post only for the server of the forum to disconnect! Loosing my page

Short version:- Want to increase the pressure of the cap as i would not think I could buy one anywhere!

1) Bend the old cap fixings upwards so the cap would be tighter?
2) Cut the rubber seal out of the old cap and fit that in first, then the rad cap?

What do you think? I do have a switched fitted now but forgot it tonight and the fan cut in to late. Bike has now done about 800 miles with this problem and i do love my bike!!

I have thought about this! I am 99 sure that the system for what ever reason does not have enough pressure in it.
However if I am wrong adding extra pressure then that puts extra load on all the seals in the engine with possible leaks!

Back to the switch....

I have found you can buy :-

1) variable fan switch thati might fit and you can vary the temp that the fan cuts in.

2) higher rated rad cap. Standard is 1.1bar and the higher one is 1.6bar.

As my temp gauge never goes over approx half way and you can squeeze rad pipes (little pressure) and so many people on this tread has said "Rad Cap" I am tempted to buy the new rad cap when I get some money as this wil raise boiling point and I could possibly put stat back in?

Any views would be really welcome!

The uprated rad cap would be better than modding the existing one.

have you drained a flushed the coolant system through

alloy+water causes furring, (not if you change the coolant regularly and use the correct amount of anti-freeze)
but if it's been left (by previous owner) to go thin by topping up with water instead of anti-freeze mix or using tap water instead of distilled water
you can get de-furring fluid but make sure it's for alloy blocks

£30 for this & £30 for that is gonna be expensive if all it needs is a good clean and flush through, once done check all the electrical connectors for the cooling system, once sure they're all ok and if the fan, gauge, pump, rad cap and thermostat all work then it has to be a sensor

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Hogdigerdy Dog wrote:have you drained a flushed the coolant system through

alloy+water causes furring, (not if you change the coolant regularly and use the correct amount of anti-freeze)
but if it's been left (by previous owner) to go thin by topping up with water instead of anti-freeze mix or using tap water instead of distilled water
you can get de-furring fluid but make sure it's for alloy blocks

£30 for this & £30 for that is gonna be expensive if all it needs is a good clean and flush through, once done check all the electrical connectors for the cooling system, once sure they're all ok and if the fan, gauge, pump, rad cap and thermostat all work then it has to be a sensor

Yes yes and yes. The cooling system is flushed today, clean as a whistle! I have not yet put stat in and the only thing I have not replaced is the temp gauge sender ( if anyone has got one to spare)! They are £35!

I have come across a company that you can fit a adjustable fan sensor that you define. This sounds like s great idea is much cheaper than the temp gauge unit.

Mr Yamaha says it's rad cap, or head gasket or cracked block, end of story!!

The only thing that bothers me is that I am unsure if it has always been like it or not? The first time it happened was after a few days of fiddling and messing with the carbs, everytime I started it, it would rev to 8k or so I I would fiddle to get the revs down. This kept happening for about half hour when I noticed all the water on the floor and steam coming out of the expansion tank. I thought I may have done the head gasket or something but have since thought surely these engines are tougher than that? If it had been 12 to 15 k then maybe but since sorting the carbs out it has been just great and I have done over 800 miles since then!

The only two things that seem amiss are temp gauge only going half way up and the boiling that happens at that reported temperature.

I think I might get a variable fan switch and ride it a good 500 miles to give the coolant to settle in. Then buy a block test from e bay that tests the coolant for compustiion gases that will tell once and for all if it is head or block leaks.

When I first spoke to mr yamaha I explained I have the 1st engine fitted with various parts of the 3TJ on it. He said one reason may be that it could be a compatable problem that I may have to live with or find a way around!!

I would love to get this sorted but it looks that I may have to live with it! But in every other way I love the bike to bits and gives me so much pleasure I would be lost without it !!