I am with crusty,

Any hesitation to settle in idle qiuckly is sure sign of a lean idle mixture. Lean idle makes room for the possibility of engine cutting out without notice.
A smaller prop will worsen low load burble. I do not think a 23x8 twoblade small on any 50, as demonstrated by the prop ripping.
Low load burbling stems from two sources:
1) lack of scavenging gasses, which does not allow the spent gasses to be expelled sufficiently to fire on each cycle. This is the main burble cause. There is nothing that can be done about that. Going TOO LEAN will restore smoothness up to a point! Hey... it's a two stroke engine.
2) overly rich mixtures.

On some engines it is well possible to go too lean without the engine providing due feedback. Best idle setting is where the engine drops down slightly if the throttle is closed, and then ragains a few rpm.
Failure to settle down quickly is a sure sign of lean idle. This can be compensated for by making the load setting richer, but it is not the way to go.