I have completed a refresh on my machine (teardown, sand blast and paint parts, replace worn stuff, etc.). I disassembled and cleaned the carb per Flying W.'s tutorial (excellent info!). I also adjusted the intake and exhaust valves per the service manual. Machine is completely stock. I fired it up for the first time since it was reassembled yesterday and it will not idle.Once I got it warmed up, I ran it around the yard for a while to get it completely up to operating temp. It runs great, but still wouldn't idle. I played with the air screw; did not affect it at all. I pulled the spark plug and it is really black (rich). Installed a new plug and fired it back up. If I hold the throttle open a little, I can keep it running, but I noticed it was smoking a little and smelled very rich (black smoke, not blue). I don't believe there is anything wrong in the carb, but I may have missed something. It is also possible that I adjusted the valves too tightly. Any thoughts on a cause?