Remove this screw and pop the cover off of the carb. There is a small screen that sometimes gets plugged with gunk from the fuel. I cleaned mine on my 036 and it ran like new on the factory carb settings. You might as well change out the fuel line and filter while you are at it. Carbs are cheap if you have to replace it. There's nothing worse than a saw that won't run right when you need it.
I just replaced the fuel line and filter on my brothers 029, since the fuel line had some cracks in it. The saw runs like new again. I have a lot of hours on my 036 and I wouldn't use anything else. It's a simple saw to work on and has cut all of my firewood for 10 years so far. I've only had to replace the drive sprocket due to wear, the fuel line and filter, and I put a new bar on it last year since the sprocket in the bar was shot. Good luck!