I purchased a Poulan Pro 4-cycle trimmer (PP428S) in September of last year. I ran it after putting it together in September and it worked great. I think I also started it once around December-January and all was well then, too. I tried to start it today and it would start without any trouble (following the instructions) but after letting the engine warm up and turn the choke off it would stall. I could run it at half-choke, but if I give it too much throttle, it dies. If I let off on the gas and give it full-choke it sometimes stays running. I've kept the motor running for upwards of 2-3 minutes, but it's boggy when I give it gas. The engine will run up high on the RPM's for a while at half-choke, but then gets boggy and I need to let off on the gas to keep it going.
I'm using fresh gas that's 92 octane. I have not yet tried replacing the plug but will do so and try again.