On one stroke the intake valve should open with the piston going down, when the piston comes back up to top dead center, both valves should be closed, piston goes back down valves closed, as the piston comes back up the exhaust valve should open.
Intake valve is the bigger of the two.
Does one valve open the same height as the other?
also, with the piston at the top of the cylinder, push down in the middle of it and see if you feel any play up and down without the crankshaft moving...