Vx800 poor compression

I have recently been rebuilding a vx800 but I seem to be having a problem with the front cylinder it is showing "0psi" that's right nothing nada not even a peep the rear is sitting about 100psi I've had the head off and reground the valves put it back together with new gaskets and it's still showing nothing 
Anybody got any ideas?

Are the carbs on the bike? if so make sure the throttle is fully open before you do a compression test. Is the piston actually going up and down and is the cam actually rotating when you turn it over??

No carbs on the engine it's just a bare engine in a stand. The piston was moving up and down when i had the heads off to do the valves. When I hooked it up to a battery and turned it over you could feel a small amount of pressure coming from the exhaust but the gauge was still reading "0psi" I thought many the gauge might have been at fault but it worked fine on the rear cylinder.

Valve not closing properly or you forgot to fit the piston rings

Ha ha the piston rings are definitely there I'll need to check the valves again but I can't see why it wouldn't close