Carb Tuning

I hear about that trick years ago. Just recalled it now after reading this. But I recall it a little diff.

Rev the motor up, yeah 4000 rpms and while the throttle is open, throw a clean rag over the carb and open the throttle more. Motor should stall. Repeat a few times.

Now I haven't done that for 20 years, but I do recall it. Does it work ?? Can't hurt..