Could it be a burned valve? I know that doesn't usually happen on the intake side, but it sounds like it. Also, it's very possible that a spec of carbon or something is preventing a good seal.

I just did my valve stems but I pulled the head out. I did find that on a couple of valves I had to put a piece of pipe over the valve spring and smack it gently with a hammer to unstick the valve keeper.

You could also try spraying some oil down into the cylinder in the hope that you might get lucky and get some oil into the valve/seat area and help make a better seal. Can't you just unbolt the rocker arms, then it wouldn't matter where the engine crankshaft is? (admittedly I've got a different engine).

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