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Discussion Starter · #1 ·
I have a 2010 sportsman 500 original owner with 90 hrs on it. It has never been in deep mud or water, hardest work it has done is plowing my driveway. Its had a very easy life so far. Today I fired it up and made one pass with the plow, after backing up I got off to move something and the atv stalled. When trying to restart it, it back fired out of the exhaust that sounded like a 12 gauge.

After all day of screwing around with it, its still wont start and backfires so loud that Im almost afraid to try and turn it over. I drained and added new fuel, blew lines out, it has spark. One thing I noticed is that it only back fires when the choke is closed. With choke open it will turn over all day with no issues. But with choke closed it almost sounds like it gets bound up, it stops turning over and once you let off the key and try again it will turn over again which usually ends in a backfire.

Anybody have any suggestions? Drives me nuts, this is the first atv I ever bought new and have always had some type of starting issues with it staying running until its warmed up. The other atvs I have start and run with no issues, they just don't have a plow on them which I need very badly now.

Any help would be very helpful!! Thanks
 

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Whay kind of fuel are ya running and have u looked at the plug yet

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Backfiring is a lean condition

Somehow not enough fuel relative to the air coming into combustion chamber. So causes could be water in carb (have you drained float?), stuck needle (cleaned it out with carb cleaner?) or worse stuff like low fuel pressure (removed fuel line after pump to see how much moves when cranking engine?). Get yourself the service manual and go thru the check out process methodically. You'll find the issue and it'll run better than ever. Best of luck!
 

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^What he said

Is it heated where you keep your atv?

I'd throw a new plug in for good measure but Chances are its not getting enough fuel. Turn the fuel valve off, pull the supply fuel line hose off the carb, place cup or bucket under hose to catch gas, turn fuel valve on, hit start button. Fuel should gush out. If it doesn't the you have a faulty fuel valve or a clogged hose. If all is good:

Pull carb off, take apart until you can't take it apart anymore (take pics as you take it apart for reassembly),clean every part nook and cranny EXCEPT ORINGS AND GASKETS. Reassemble, install carb, see if it will start.
 

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Somehow not enough fuel relative to the air coming into combustion chamber. So causes could be water in carb (have you drained float?), stuck needle (cleaned it out with carb cleaner?) or worse stuff like low fuel pressure (removed fuel line after pump to see how much moves when cranking engine?). Get yourself the service manual and go thru the check out process methodically. You'll find the issue and it'll run better than ever. Best of luck!
Backfiring can be a rich or lean condition. If it backfires thru the carb it is too lean....if it pops out the exhaust...it's too rich.
 

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Discussion Starter · #6 ·
Thanks guys for the responses, One other thing I forgot to mention I have the flashing wrench. I'll have to look into checking the code Im not really sure how to do that.

I did change plug and pull line off carb, I had fuel going into carb. One thing I didn't do was drain bowl. Wasn't sure of how to drain it, it didn't have the normal screw with little spring. Or at least I didn't see it. I did pull plug and turned it over hoping if there was water in the bowl it would get blown out.
 

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Fuel flow is good so cross that off. New plug and you verified you had spark so that's good.
You gotta check into that code and see what the machines trying to tell you.
If its just a maintenance code then I would take the carb apart and clean it REAL good. Chances are it needs a good cleaning, then you can visually inspect the guts of it and see if anything needs replacing. Usually its just the needle and seat that ever wear out. Also check your carb boot for cracks. Make sure the air filter is clean and the lid to your airbox is on properly. I've seen these machines do crazy things with missing lids or modified air intakes. Also would be worth checking the oil level to make sure no gas has seeped into the crankcase from a faulty needle and seat. Have seen that before too.
 

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also check your air box make sure cover is on tight...look at filter also...no critters took up a home there...
 

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Discussion Starter · #9 ·
Just drained bowl and flushed carb with carb cleaner and air..still nothing. Like I said this atv is pretty much new, never riden hard. My buddies bust on me because its show room condition yet. I know that really doesn't mean anything about whats going on inside carb. Tried checking codes for flashing wrench, manual is very basic doesn't really tell you how to read it. The only thing I saw that may be a issue was volts were 11.2. Its on a trickle charger 24/7.
 

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If you have a carburated motor, it won't have a code.
After you get the battery charged up,Make sure carb. is clean and verify engine timing is correct.Just in case you sheared off the flywheel key.
 

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Discussion Starter · #11 ·
Thanks everyone for the responses....I think I may have sheered off the fly wheel key. I just did a compression test and I've only got 45 lbs of compression. So I'm hoping it just jumped out of timing and I didn't bend any valves or break anything else.
 
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