Engine running unevenly, bike lurching

[jdrider]

Hello all, I'm new to this forum. Hoping I can get some help.

My 2002 gx250 was in storage in my garage for the winter. When I took it out of storage I drained the bad gas, checked the line and pet cock, and filled the tank. I also changed the oil and gave it a new battery as the other one was pretty old.

It starts ok but not great. I have to let it warm up for a long time and still have to leave the choke about 1/4 out for a while, maybe 10 minutes. It idles rough, kind of sputtering. When I'm in gear it will lurch forward and seems to run unevenly. I've messed with the throttle stop screw which was probably not the best idea since I didn't use a tach. I can't tell now if it's too fast or slow.

My first thought was "dirty carb". I figured the old gas was probably not great for the fuel system. I've read a couple other entries on this forum and now I'm not so sure. :??: I wanted to see what others thought before I go pay someone to clean the carb. Air filter? Spark plug? Something else?

Thanks!
Jen