i am looking at buying a nsr 150 the 1 that is in the best condition and my price range .. has a weird tapping noise when idling its defiantly a sound that shouldn't be there

when the clutch is pulled in the sound goes away and the bike runs great goes through the gears really smooth .

does anyone know if this sounds like a major problem i know that 2 strokes don't sit to well when idle but the taping just aint right

every things fine apart from when idle