It's a regular People 250, not the S250. It has at least 10k kilometers (broken speedo cable when i bought it).
It runs fine when the engine is cold. Haven't tested it in air temps below 55 degrees. It seems worse when the engine is very warm, like when the radiator fan comes on.
I tried turning the low-speed screw 1 turn either way and idle didn't increase. Idle slowed when i turned it in.
I don't know when these air filters need replacing, but i ordered a new one. The old one is below..
I haven't done much else. I didn't take apart the carb. The hoses seem in good condition, no cracks or kinks.
Could it be a bad spark plug cap? The old plug that came with the bike had a broken ceramic tip and the plug cap is chipped in a few spots.. almost as if it was hammered from the side (!). I trimmed 1/2 inch from the plug wire while i was down there.