if he doesn't believe he has one, get up to around 100km/h drop it all the way back to 1st and pull the clutch in.
While coasting atabout 100, and in 1st gear with clutch in, drop the clutch.
take note the bike wiont lock up and chatter it will just wiggle a little and smoothly slow down.
i dont recommend trying that with a non slipper equiped bike.
kawasaki calls it "backwards torque limiting clutch"