Actually it might be running lean. Too lean can stink too. I know it sounds strange but it does. I used to service forklifts at a factory that ran 5 lifts in a rather small building and CO output became a issue. More times than not when they complained one was stinking like it was rich my exhaust gas analyzer said just the opposite, that it was excessively lean.
In your case of closing the choke and the engine speeding up is a clear indication that it's not too rich. It could be running lean from either a mis-adjusted carb or vacuum leak. Also make sure your timing is adjusted correctly before working out the bugs in the carb. Timing affects things alot.
