Is the choke on when its up or down - Suzuki 2005 Vinson 500 4X4 Manual

check carb may need cleaning rebuild or replacement also check primer unit for possible failure

make sure air conditioner is not on, sounds like choke is slightly on. check that upper butterfly is open all the way.

lever down to choke .pulls plunger up .

2 stroke or 4? if 2 stroke definitely jetted wrong choking makes it rich tells me your main jet is too lean (smaller hole) you need to pull carb check jets for plugage clean jets write down numbers check dealer for correct jet size for your elevation if 4 stroke back fire thru carb indicates timing is off or bad intake valves or cam lobe worn

If you haven't taken that carb apart and cleaned it in awhile - more than likely your jets (what's used to pick the gas up out of the bottom of the carb (the bowl) are clogged up. You can pick up a can of carburetor cleaner with a wire basket inside from any major parts store specifically for carburetors to soak in. The size of a paint can & around $20. Soak the carb in that for awhile after disassembling, make sure none of your ports are clogged - air compressor gun or you can also use keyboard cleaner - air dusters. You want to verify that air can pass through all those ports properly and blowing air through them is how you do it. Carb does need to be completely disassembled to do this. The jets in the carb suck up fuel due to the vacuum the engine creates turning over. Once it starts spinning - it builds up a little suction and everything is fine. When the jets start to clog - one of the ways to force the carb to pull harder is to work the choke. The only thing that choke is doing is operating the butterfly. When the choke is on - the butterfly closes. Making all of that suction stay right there in the carb. Once the bike starts to warm up - you release the choke - and the butterfly will open - allowing more air into the system. You're running at half choke - butterfly half closed - to force those jets to pull harder. If they were clear? No need to run at half choke. Hope that broke it down for you - All The Best, Justin M. 17 South Industries, LLC

clean the carburettor..clean everything inside including the jets

If you are lucky, you might just need new fuel filter and the fuel bowl cleaned out, and maybe new air filter. If not so lucky you need carburetor rebuilt. Backfire is usaully caused by engine running too lean ( too much air for the amount of fuel present). Fuel bowls get gunk in them and the fuel needles and fuel jets get varnished up. The accelerator pump gets worn out gaskets and/or bellows and doesn't give the right amount of fuel mist when you accelerate.

Full Choke is indicative of a motor starved for fuel

The number 1 problem with ATVs is the carburetor. This could be a mixture problem... too rich will cause backfiring and difficulty starting as the carb needs more air. Try leaning it down a 1/8 turn. The choke is always intended to be used when starting; if you don't need to use the choke, the card is definitely running too rich. If you can't adjust to make it behave properly, then rebuild the carb, It's not difficult.. get a new throttle spring and float too. Ensure you place the keeper clip on the correct groove of the needle valve... where the throttle cable connects. Replace all the jets and gaskets... don;t get them mixed up. One larger jet is the primary jet and the smaller one, is the secondary. Get new screws, if the screws are a bit dog eared. Write down your previous mixture settings and start from there to adjust the mixture for starting and assure a slightly skipped idle. (Don't worry as you add throttle it will run smoothly.)

A couple of suggestions: Make sure that the gasket seal is good between carb and engine. I had a similar problem with my Cat 500 and found that the choke was sticking. I sprayed down the carb with Gunk and made sure all moving parts were not hanging up. I also put anti fogging oil in the gas to help clean jets and ports hard to clean with a carb rebuild.

the carb either needs adjustment or rebuilt most likely