Strange one, this.
Don't think it's cam chain. Can't think of anything front right inside the engine that would make an intermittent noise either.
I'd start by ensuring that the exhaust headers are secure and that you don't have any stones or such caught that might rattle under specific conditions. Check the rear header mount bracket, too ... the weld on that can fail and you could be hearing a reflected noise. Look on the rear of the EXUP housing close by the centrestand pivot.
Definitely check that the EXUP is working correctly and the cables properly adjusted. Worn/maladjusted EXUPs can cause all sorts of weird noises.
I'm assuming clutch and gearbox works as it should?