@Calum everything seems to be right. Ypvs works. I pulled out the plug yesterday, on the end of the ground electrode there were a small bit of carbon, i thought that was causing the problem. I swapped the plug, and same thing happens when the bike gets hot. Could it be pre ignition? I've read that carbon deposits on the piston could cause pre ignition when the bike heats up.

When i am riding my bike and it gets warmed up good, it starts making these ugly noises in high rpm, and they keep getting worse as the rpm goes up. I have ridden the bike for a couple of months now since the cylinder was honed and i put a new piston in it. There is no drop in power or compression. Almost sounds like ignition knocking at some point

@Calum ordered brand new radiator cap, but i have to wait for at least a week. Would it work to plug the line to the overflow so it does not fill up the bottle, just as a temporary fix?
Or will this cause big problems?

@Calum so it could be a gasket issue?

@Calum used this method https://youtu.be/QVQqqjkXjnA

@Calum applied it on the thing close to the radiator cap, where the line to the expansion bottle goes

@Calum this explains why the overflow bottle is filling up right?

@Calum https://youtu.be/MoESLzTLdd8
I put pressure on it and it just leaked out water and air

@Calum any way to check the cap? The seals on it looks good

So the coolant is going from the radiator and into the expansion bottle, ive tried to remove water from the bottle so there is just a little bit left, topped up the radiator, and then i bleeded it. Same thing happens once i put the radiator cap on.

I suspect the headgasket, so i ordered new athena gasket set. But i does not really make sense to me as the bike does not overheat and the water is not hot either.

Suggestions?