The only thing I can come up with is the bleed screw.....It should be on the bottom of the carb in line with the throat. Could be covered with a metal plug over the hole if it has never been apart before. If it's on the engine side, it controls fuel so turn it out to make the mix richer. If its on the air cleaner side, it controls air so turn it in to make the mix richer.
Changing the fuel/air mix this way will effect the entire rpm range. but is sounds like you have 2 different problems. Just as a confirmation, fire it up and just let it idle for a few minutes. Pull the plug and see what you have. If the mix is too lean, your plug will probably be white. If its rich, it will be black and/or wet with fuel.
2001 Magnum 325 with a blown engine; rebuilt 2004. Broke timeing chain 2016 rebuilt again and still running. Warn winch and Moose 60" plow
2007 Sportsman 500 EFI, Polaris Winch, 26" Bear Claw HTRs on Moose 427x Wheels. 12x7 front, 12x8 rear, QSC Clutch Kit
My Trail Machine:
2004 Sportsman 600 Twin, 25" RipSaw Tires on stock steel wheels, Moose rear box
Completed Project machine:
2001 Magnum 325 MOSE with a blown engine. Transplanted a 2005 Magnum 330 engine. Committed suicide on the trail Oct 2016. Spun Rod Bearing after oild cooler line failure. Rebuilding Engine.