Interesting clip of what can't be seen by the naked eye. Some pretty violent stuff goes on when valve bounce occurs, as you no doubt know, Ace. But for anyone who doesn't realise the implications, it can quite quickly rip the end of a valve right off, damage ridges on collets, which then let the valve stem slip through them, accelerate wear on ANY kind of valve seats and cause piston crown damage [even total destruction], as well as just limiting performance.
The AVL 500 [Electra X] suffers very badly, probably on both valves, but the inlet valve bounce is the one restricting the RPM's - I held one flat out [WOT] in neutral on the centre stand, at first believing there was a built in rev limiter somewhere. There wasn't
On a dyno run, clouds of fuel mixture blowing back from the [open] end of the carb, accompanied by a very loud and hard version of a pinking [pinging] noise at around 5,800 RPM, made the penny drop very quickly. followed shortly afterwards by the inlet valve itself !!
A big bang will be on the cards sooner or later for anyone trying to rev much past 5,500 RPM on a standard engine because of this 'inbuilt feature' which prevents the full use of the porting, squish set up and pretty robust bottom ends that these machines are already blessed with.
B.W.