Poulan Pro chainsaw starts, idles extremely fast, but dies when I hit the gas...

Hello, I have just found this great site, looks very helpful. I have a problem with My lawnmower\lawn tractor, its a Husqvarna LT125. It was running fine last year and I started it once about a month ago and it started OK for having been sat up for about 5 months or so. Last weekend it wouldn't start, I thought it was the battery since it hadn't charged all winter, so I connected it to my car battery with jump leads and it started OK after a little turning over. I cut the lawn and then the engine started to loose power and eventually cut out under load. It never did this once in the year If had it. I took it it and cleaned the air filter and spark plug, it started fine with just the battery and seemed to be running great for a while, then the same thing, it cut out under load, at this point I suspected poor fuel not I had put fresh fuel i but there was some in there from last year. When I disconnected the inline fuel filter I saw it was blocked straight away so I replaced it and filled with fresh fuel. The engine would not start with the battery , just cranked and cranked, it did this for maybe 5 tries before the battery started to fail. I connected to my car battery again and continued trying to start, eventually I could hear it trying to fire just as I stopped turning the key, a few more tries and it fired up and started running. Finished cutting the lawn with no loss of power and all was well, no I have tried to start it a couple more times and each time I need to hook it up to the car and its takes a lot more cranking than it used to by far, last time it only started after I stopped choking it (it always used to need the choke). So question, Why has it become harder to start since replacing the fuel filter. Thanks in advance for any help

ok.. i'm so happy to find [URL="http://www.doityourself.com/forum/outdoor-gasoline-powered-equipment-small-engines/453543-craftsman-eager-1-4-5-carburetor-rebuild-reply.html"]this thread[/URL].. but it's been a while and hopefully people here can still help. i read through the whole thing.. took the carb apart and replace the big o-ring and use carb cleaner to clean it out. the re-assembled. it started perfectly... mowed the grass and done. here's the weird part... winter.. didn't mow the grass and just last weekend.. tried to started it up.. it was just fine.. till the blade hit the grass. went for a while and stopped. the grass was short.. not long or rough.. so i don't think the grass is long enough to catch it to get the blades stuck. what should i do? replace all the o-rings? also, i was using a 10W-30 in there, which i saw was ok for California climate. is there anything else i should clean out? hate to take it apart each time to mow the grass... thanks!!