OK thanks will go over it all tomorrow, what's best way to make sure it's properly bled also? Thanks!
Fill the expansion tank no more than the upper level, and fill the rest really slowly via the thermostat cap up front, just let it trickle in to avoid bubbles or air pockets.
Once it's filled to the top you can actually start the bike with the thermostat cap off and let the coolant circulate, and in the process hope that any excess air escapes to the top.
Don't give the throttle a massive blip or you'll end up wearing it as the water pump increases the flow.
Just let it tick over and keep an eye on the fluid and see if any bubbles pop up and the level gets lower.
Remember you'll probably only get about 2 minutes of this before the fuel runs out, unless you find a way of keeping the fuel pipe connected, but it's normally enough time anyway.
The main thing is using the Radflush to unclog the coolant engine/radiator channels in the first place though.
What i normally do, especially as the weather right now is a perfect temperature, is leave the Radflush in for a couple of days topped up with clean water, so that the bike heats up and cools down a few times, and the Radflush really gets to circulate and clean the system properly.
Obviously this is not ideal if you do long motorway runs, or if the weather is too hot or too cold, as the coolant/anti freeze covers both ends of the temperature scale, that's why the temperature right now is perfect (i presume you're not in the Scottish highlands and you haven't got snow?)
Once you're done flush it all out with a hose then refill with a decent coolant, i prefer the premixed bike stuff myself, others will mix their own 50/50, but that's just personal choice.
Once it's all done and all working fine again you should literally be able to leave it alone for ages.
Every now and then if the bike's on the centre stand i'll check the expansion tank level but it rarely moves between the lower/upper levels once the bike has cooled down and that means all is good.
If you suddenly see it's empty then either the above procedure needs doing, plus you can also check that any jubilee clips around any water pipes are tightened up correctly, especially around the thermostat area.
A good trick is to wait until dark then use a torch around the appropriate areas and a suspected coolant leak can be seen much easier, as the coolant will shine under torch light.
I'm not ruling out the 'Dudes suggestion of an iffy thermostat either, but from history i've always found them to be quite a reliable part of a bike.
Whether the expansion tank is empty or not will be a huge indication either way.
Don't rule out a knackered water pump either, if the water simply isn't circulating at all then that's another reason for overheating!
While the thermostat cap is off and the engine is running you can VERY GENTLY give a bit of revs and you'll see the fluid move if the pump is functioning okay, just don't give the throttle a full handful.