u/Apprehensive-Biker

Rides fine all rev range until about 30 mins in then it splutters to a halt …. Leave it 5 mins and it’s back to normal
I know this is probably fuel related but having hard time trying to figure out what to do next

As I’m driving the bike spits all it’s coolant (water) out the top of the rad , I haven’t used real coolant yet since I’m just testing things but it doesn’t have an overflow tank behind the rad , oil isn’t mixing with it either , any advice? I’m losing 300ml after a short ride