if you stick your finger over the exhaust outlet on the head, it sucks your finger in on the compression stroke.
If you are turning the crank the normal direction that should NOT happen. Any time the piston is rising you will only get outflow on the exhaust during the exhaust stroke, and directly following a draw on the intake as the piston then travels down.
If once past TDC on the POWER stroke and the piston is traveling downwards you feel a draw on the exhaust, then your have a leak in that valve. It may be slight and allow for compression when turning quickly, but will not help you build enough for a sustained light off.
You should be able to feel good compression even if turning slowly. That indicates good seals at the ring and both valves. You may have to inject some oil or fuel to initially help lube and seal the ring. Don't spin it completely dry.
Off to get some lunch and clean the build room. Will check back during the day. My vacation started so will be able to stay active till after the Holidays.