I'm not an engine guy, and recommend calling Chuck at Performance Cycle Worx or if you are far from ATL I might know someone else. Unfortunately, it sounds like something in the transmission is damaged, something like the shift fork or the dogs on first, or maybe even the gear itself. I was told to always try to shift up into the next gear from a false neutral or come to a complete stop and then shift into first. I wasn't provided with the reason why....but that is what I always try to do... Sorry sir. I'm sure you didn't want to hear that.