If the carb. was assembled right I would suspect the Carb. out of adjustment, (too lean on the high side, 1/8" or so turn counter clockwise will richen it up if it can be adjusted?) or carb. still dirty in the medimun and high jets. I would also check jug/crank case cover and muffler mount screws for tightness. (may have a massive vacuum leak? not likely but I would check them anyway)

Check the exhaust port for deposits yet? Free and easy.

You use compress air after cleaning the inside of the carb to blow dry it?

Aha: Check Fuel Filter 1st . Remove Jets , inspect all ok ? Clean Jets with Carb Cleaner Spray reinstall to 1-1/4 to 1-1/2 turns out . Also put some carb cleaner in fuel System approx 1 Oz. If diaphram within carb is ok you should be up and running within 30 Minutes . As always use Fuel Treatments for Storage and Annual Start up . As recommended by other Forum Members new Lines and Plugs as required during Routine Inspections. Let us know how you make out !