I found the article very informative about replacing the seals on my Crosman 760. I also found out it was made in July 1970. Thank you. After replacing 3 of the 4 seals and reassembling the BB gun, it still will not pump up and hold air. The 4th seal in the replacement kit just did not look compatible. I noticed when I took the brass valve apart the spring was corroded a little and only one plug came out. It looked like another piece was still up inside. Any suggestions?