If you are certain the carburetor is clear and not running lean, I would check for air leaks around the base gasket to see if it may be leaning out that way. Are you using regular fuel and not premium?
Have you checked the flywheel key for partial shearing, throwing it out of time? Otherwise, the most likely thing is a bad-seating exhaust valve.
If you are dripping gas out the carb, that's either a misadjusted or damaged float, or a bad needle and seat. That'll be an easy fix.
Since it starts easily, the flywheel key probably is okay. The sputtering could be due to the extra fuel in the carburetor, or you may have an exhaust valve sticking which would also account for the hot muffler.
How much time is on the engine?
Something I forgot to ask is what temperature you're running it in now? Unlesss it's cold and snowy, the muffler may be margianlly normal if you're in a warmer area and it's not well-lit. The snow engines have shrouds around them to help contain the heat.
The valve seat will need to be re-cut using a special cutter that puts three angles on the seat, a new valve installed, and the base of the valve stem ground square in a grinder to get the proper clearance using a special jig. It sounds more involved than it really it, but without specialized equipment, it's really a job for a service dealer to perform.
Yep, to much for me. One more question. Can the seat in the be pushed up to far that the needle isn't sealing?
Not likely. The seat will stop against the body of the carburetor. But it needs to be installed with the tiny ridge toward the carb body, or it sometimes slips back down. The direction of the needle hanger makes a difference too. The open end of the hanger wire should point to the choke side of the carburetor. Finally, the float does need to be adjusted. There is a bendable tab the needle hanger wire rides on that can be bent with a small screwdriver. This controls the point where the fuel is shut off. With the rubber bowl gasket removed, the edge of the float on the side opposite the hinge pin should be 11/64" away from the carb body. A drill bit makes a good gauge.