Might want to take a bowl off and peer inside. I bought a 650 DP off someone who claimed it had been sitting on a shelf for years, got it home, opened it up and it was completely ROTTEN. Seriously, the body of the carb was literally disintegrating into a powdery mess. Tried cleaning it but the corrosion had destroyed the carb. Never got my money back.
Core Carbs are not worth much.....I pay $25 at swap meets for them....one sitting for years is a core
You can buy fully rebuilt ones for $250 that look like new
If its your buddy....gotta go cheap