Anyone know anything about motorcycle repair?

i just bought a 2006 Nina 250r LIKE NEW (showroom floor looking) with 177.9 miles on it lol. it cost me $2000…BUT, the people who owned it hadnt used it in a while and it sat in their garage. the battery was dead, so after going through HELL to find a new one and pour the acid into it and charge it, i put it in, and the bike starts great…with the choke on. once i take the choke off it instantly stalls. EVERY one seems to agree that this is simply (or i hope simply) because the gas sat in the tank and clogged the carbs. i even called kawasaki and thats what he said. what is the best way to fix this without paying ”$95/hour for 4 hours.” can i use a liquid carb cleaner? can i let the bike idle with choke on for longer and maybe have luck? is this a bigger problem than im aware of and i screwed myself with this purchase?

this is my first motorcycle and i know NOTHING about them. i just thought this was an excellent deal and my uncle (a biker) came with me and said it sounded great (running with choke) and looked amazing! PLEASE help!!! i cant afford another $400, im hoping this can be a SOMEWHAT easy fix!