Troy-Bilt Bronco rebuild

All right I'm rebuilding an old mower that didn't run I reran the lines cleaned out the gas tank put a new carburetor on it and it started up but it stinks really bad could it just be maybe some spilled grease on the exhaust or clean out the cobwebs or I mean but it's stunk bad and it's kind of just smoking pretty good so I don't think it's just cobwebs ideas? It's a Kohler motor color courage I do know I'm going to have to take off the valve cover and put a new seal on it because it is leaking oil pretty bad I had to do that on a old Cub Cadet I had to other than that I really can't figure out what the smoking or smell is it's can't really identify it be honest with you and good smell like grease burning but why would it smoke that bad?