Won’t start

[Mark W]

I finished my bike yesterday and went for a few rides and everything ran great. I returned from a long ride and it wouldn’t start so I let it rest and it started and when on a long ride, now it won’t start, it sounds like it is going to start and bucks and engages a little. It seems like maybe clutch is slipping? Photo:

 

[Venice Motor Bikes]

Is it a new engine?