If were my bike, I'd do some inspection. Pull the primary drive inpsection cover off and have a look, if nothing, I'd pull the whole primary drive cover off and check out from the compensator shaft all the way back to the clutch for irregularities.
It doesn't sound like the same problem to me, but when I bought my bike the previous owner left the spacer out for the compensator shaft and the front drive sprocket was way too loose. The primary chain was slapping against the cover.