There are multiple modes of failure so it's hard to tell.
But most likely you will hear a noise, fer goods sake!!! pull in the clutch! and let her quit. Coast to the side of the road and check her out... not that you can put your eyeball anywhere and say 'cam chain' with any certainty.
1st, plunger will separate from the housing and start to grind.
2nd, the chain will get loose and rub on the case.
3rd, the plunger spring will slip out and start bouncing around (yep quite dangerously) if ye auld spring gets caught in any of the gears... a sudden stop ye will come to hopefully with knees securely gripping the tank least you learn how to fly and why gravity is cruel.
I believe it was JOG that said dam spring or spring bits as the case may be can lodge somewhere and prevent the clutch from operating.
So, if you've been trained by the FN stock petcock to put it prime and hope for a restart in a second or two... lemme dissuade you from further following the practice.
Have a nice ride