one thing to keep in mind about the decompression valve is it will pop back up if you get any combustion at all, sometimes without being very noticeable. If your pull cord is stopping mid pull then there's a good chance the button popped up between pulls and you weren't aware. Try getting in the habit of checking it in between every pull. A coworker of mine broke a finger trying to start an 088 when the pull cord stopped mid pull. If you get a "tremendous pain" in your wrist after this has happened my guess is that you probably injured it when this happened.