Basically the same thoughts I had..., "how did it break and did I do it"? Sounds like there is a common issue however. I'm not a trained tech just to be clear on any advise here. My ski probably had been running for a while with no issue involving the check valve being broken. I assume the valve is for preventing oil from flowing backward into other air lines, etc. when the ski is upside down in the water. I never had a roll over so It never had to function. A new part had to come from Vintage and was $38+, and took a couple weeks. You have to buy the entire oil filler housing that will have the small part in the bottom that the check valve slips on to. I ended up plastic welding mine back into the old oil filler part as I wanted to go riding..., and it works fine as before. The new part finally came, have not re-installed. Probably a 30 minute fix. I'd plastic weld it since you are familiar with that process unless the owner wants to bite that $38 bullet. Be sure to check your check valve by blowing through it, one way allows air to pass through, other direction does not as mentioned in the above string. Make sure it's clear of any oil.
