i have a old craftsman 9hp snow blower with a similar problem, has 9hp kohler motor,.
when i got it there was a big surging problem with it. took off the bowl and cleaned everything up. ran better but still had a surge problem,. bought a new carb for $12. didn't surge but barely ran, acts like it not getting fuel. dropped it off by my brother in law who works on small engines on the side it to look at it. been there for 4 months he hasn't had time to look at it yet.