Definitely sounds lean as neobart posted.
I have found that my M26SS in my AS likes to run hot for decent power (250-270). What are your temps? I also had many air leak issues out of the box with my AS. The fuel filter seal was destroyed. I replaced the whole filter since I had a spare. The carb neck leaked, the LSN leaked and the backplate leaked. I sealed the carb neck, backplate and lubed the LSN seal with associated green slime.
Now it doesn't leak, but it still runs hot. It runs pretty strong though. Quite a bit of power, fairly economical for fuel, but starts hard and runs warm.
I don't know why it starts so hard either. It has plenty of compression, I've tried new fuel, new plugs, different temp plugs, but to no avail, it will only start if I slowly turn it over. If I rip on the cord like I do every other engine with quick 8" pulls while giving it a bit of gas, it won't start. But, if it's properly primed, I put the heater on it for about 10 seconds, then slowly pull the starter cord, it will pop and run after a few slow pulls. It's very odd... That's only for a cold start though. When it's hot and stalls from being on it's roof, short quick pulls like my other engines gets it going.
It's a very odd bird, but I really enjoy running it.
A little tip, get some extra fuel line and run your lines around your rear shock tower. This will give you more than 15 seconds of run time when your on your roof.