Just repaired my father four wheeler he was letting it rott after my brother locked it up turned out to be just the drive belt broke.

it was sitting up for a year so I cleaned the carb as good as I could couldn't get the floats cover screws out without striping them.

Problems

won't idle have to give it gas to run
runs great full open but backfires when letting off gas and at low rpm
dies at around 1000-1200 rpm

haven't changed air filter or fuel filter

 

before looking any further, change the obvious first, fuel filter, air filter drain all the old gas including the fuel bowl if you haven't already and fill with new gas. Put a new plug in her and then see how it runs.

By the way, what does the old plug look like?

 

I agree. Do the obvious first. Gas goes bad and varnishes the carb. The good news is you don't have to throw away the old gas. I've mixed it with a tank full of new gas to dilute it in my truck and had no problems at all with it.

 

could be that the float is varnished up or not set right letting too much gas in. also is the idle and fuel screw set correctly. if its backfiring andf the plug is wet then its running too rick and igniting the excess gas when you let off it. just a couple of idears.

 

usually popping or backfire on decel is a lean condition. Does it help to run with a little choke on? If so ,then there is a good chance you will have to tear apart the carb and do a good job of cleaning all the jets an passages.

 

the backfiring can also come from the ETC Electronic Throttle Control. This can cause it not to idle and to back fire when letting off the gas. The ETC is on your right handle bar with the throttle. They can be touchy to adjust.

 

Found the problem it was the contact switch in the throttle cable seems that there is to much slack in the cable I put a piece of electrical tape between the contacts and it idles fine after a little carb adjustment. The backfire was the contact touching then me hitting the gas causing the engine to fire back.

 

Now you need to adjust the cable housing. Follow the cable down from the throttle and about half way down to the headlight pod there is an adjuster that is covered with a rubber boot. Slide the boot back and adjust the cable so that there is about 1/8 inch free play at the thumb throttle. Once you do this you can remove the tape inside and you should have more power since you will be able to open the throttle all the way.