Be careful if you are running it stationary, don't want to over heat it. If you are going to run it much stationary use a couple big fans blowing on the engine.
The discharge and pulse does kind of sound like valves but unless you did something to hurt them I doubt it at 7,000 miles. Did you check all the air passages in the carb body when you cleaned them? also take a good look at the diaphrams on the top on the slides.That sicky slide makes me wonder if something else isn't dirty too.

I learned all I need to know about life by killing smart people and eating their brains.
Eat right ,Exercise ,Stay fit, Die Anyway!