Have him check on the idle mixture passage that aligns with the mixture adjusting screw. It sounds like the carb isn't flowing any mixture through the low speed system. Also try this- - - -back the idle mixture screw out 2-3 turns, rev the engine up to around 1500-2000 RPM and slap your palm or a big rag over the carb inlet. Do this several times. Sometimes, the heavy choking action will draw liquid gas through all the passages and flush out debris that's clogging them up.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!