I have a HRC expansion tank, and a new 1.1 bar radiator cap....... Yet when i take my bike out for a blast, it seems that too much water enters the expansion tank and some comes out?
My other problem is when the bike cools back down, not all of the water that expanded to the tank returns to the system????

leave it to find a balance. I see prob an inch or less in my res tank when cold..and it has peed out a bit too when really really hot.

you don't want a lot of water in the res...just a little bit - so run it a week and it will find it's own level

Took mine 3-5 heat cycles to find the correct level, it will sort itself out eventually.

This is my level from warm, when hot it doubles in volume. It has only ever over flowed when it was first fitted (as you are experiencing currently)

Thank you guys.
The overflow pipe comming from my BIGGER upper radiator is pretty thin to be honest, i might up grade that to something with a larger diameter as i think the water is entering at too higher pressure from this small pipe i have and squirting straight out of the expansion bottle's over flow pipe.
Also i'm a little bit stumpped as to why the system isn't drawing the water back into it's radiators when cool (i have a new cap) maybe i have an air pocket, i'll get bleeding again tonight :D