I have the same saw, assuming you meant AVX not U, but probably the same thing. got it on craigslist for so little I felt guilty about it later. looks like it was hardly used, has been my most reliable saw up until a few weeks ago and it suddenly stopped starting. Thru out hte air filter, grabbed a new box of em, and realized I'd ordered the wrong ones a while back and now i haven't been able to try again. My point is it has been a surprisingly good saw considering what it costs and how hard I've pushed it. maybe 3-5 cord of hardwood thru it, nothing more than two air filters. that said, the airfilter on this thing does like to work iteslf loose, and let crud past, so my guess is if it wasn't just the dirty filter, that its that some dust made it into the carb. its on the table slated for a clean out when i get a chance. My only real complaint about this thing is that the anti vibe is super soft, so it is crazy easy to go sideways in a cut because the saw is walking around when you lean on it. basically can't use the dogs on this thing but just rely on the weight to get the cut done.
if yours was stored with gas in it, personally I'd just pull the carb apart, clean it and put it back together with the old gaskets if they don't crumble, replace the air filter and give it a go.