It is nearly impossible to tell much from that video . We know nothing about the engine and it's intended use other than it's on a tuned pipe . Knowing that an engine using a tuned pipe is intended for high rpm use , a video of off idle use tell us nothing . Piped engines are tuned for max desired rpm range or " up on the pipe " as commonly described . Low or mid range operation may appear rich or lean and means little as long as the transition from low rpm to high rpm is correct .
Regarding it no longer starting .. well ya can't phone that one in . Someone has to put there hands on it to see what the problem is.