Did you check your bushings? The flap should fall open on its own without the spring. From your pictures, it looks like the spring is moving around the shaft rather than the shaft being moved by the spring.
Yes, it operates very freely. When I "clamped" the tang against the pin ( see earlier post and pics ) it opens and closed as it should using a heat gun ( opens around 115 / 120 degrees) . I "cycled" it several times and it operates as one would expect. I'm stumped. I'm kinda hung up on the fact that "Uncle Brad" youtube video shows a spring that has a loop that wraps around the pin. I checked and rechecked the spring wind direction and orientation and its sure looks correct.
