Haven't used my Craftsman chainsaw since September. Took it out to grab some storm-downed trees. It started fine, but would die when I hit the gas. After an hour with many attempts I finally got it going, but it didn't have it's usual power. Cleaning the air filter didn't help. Spark plug was pretty dirty, so I'll get a new one and see if that fixes things. Any thoughts? This is the first time it let me down. Somebody else will probably get the wood that I didn't cut.