My Fs85 "pro series" weed wacker starts great when cold, I choke it and pull the cord about 2 times, it sputters and then starts right up after I open the choke. However, when the engine is warm like after I've been using it for an hour or so and then shut it down, it's very hard to start. This has just been happening this spring, it's a 4 year old unit owned since new. I've never done anything to it in terms of maintenance except for a fuel filter last year. I just use it for my own property probably about an hour a week during the summer.