Usually lean. Possibly slightly rich combined with an air leak.
It is not likely to ever happen with the electromagical ignition system on these bikes, but a combination of a low density mixture (closed throttle deceleration) and lots of ignition advance will cause popping too. Anyone old enough to remember the pre-49 Fords with the vacuum brake distributer?

Let's hope there's intelligent life somewhere in space 'cause it's buggar all down here. -- Monte Python