No doubt the people here will want to help, but we will probably need more information. How many miles on it, any engine mods, has it been badly dusted or flooded in a river, maintenance up to date, etc.
I will take a stab, though. Have you removed the fuel and replaced it with new, clean fuel from a different source? I have rescued several quads, a boat, and a car or two by simply replacing the fuel.
The first thing I would look at are the spark plugs. Pull them and do a visual inspection. Generally a fuel issue doesn't cause the symptoms you describe.....the typical plugged fuel filter or weak fuel pump "usually" doesn't cause any issues at idle or backfires, rather just low on power when accelerating and slow top speed with some hesitations..........keep in mind I said "usually".
It has 6100 miles. My son in law had problems with it about 2 years ago. Don’t know original problem but I’ve cleaned fuel system and replaced plugs. I did find an air leak under the throttle body. It starts now but idle seems too low dies after a few seconds