What do you mean so tight it cannot spin? Can you elaborate a bit please?

I have noticed a few things -

Flipping the bike upside down and spinning the crank - looser chain will start to pull the crank around, tighter chain won't (the crank will just stand still and freewheel).

Same goes when walking the bike, the pedals will turn. Of course only until my clip/strap hits the ground, then it will start to freewheel.