help me with my 1997 500 polaris sportsman

[jamison1969]

I have a 1997 500 polaris sportsman and it wont start, started it up and drove it for 2 min and turned it off and went to start it again and nothing but back fire, cleaned the carb out good and it has comprestion and spark, drained the gas and put in fresh stuff and tried it again still just turned over and back fired, can any one help with this ????

[Ajmboy]

How did it run when you had it running for the 2 minutes? Did anything happen?

[Stoopidbot1]

Welcome to the site, Valves???

[jamison1969]

How did it run when you had it running for the 2 minutes? Did anything happen?

it ran great, we were going ice fishing and we took it off the trailer and he took it down the road for a quick ride came back turned it off and then we loaded the ice shack up and went to start it up and it wouldnt start, just back fire ???

[jamison1969]

Welcome to the site, Valves???

nope not the valves ????

[GEARHEAD01]

it could possibly be to lean fuel mixture, or a fouling plug, or a bad battery. I would try putting a 12v boosting unit on it and then try it. if that does not work pull the plug and check it. it should be dark tan or brown depending on your oil setting. For the price i would probably put a new plug in it and make sure of proper gap. if that does not work, try choking it to start it. Did you put a carb kit in it?

[jamison1969]

The first thing i did was drain the fuel and put in new gas and put new plug in, there is nothing wrong with the battery and i have tried just about everything. No i didnt put a carb kit in. ????

[GEARHEAD01]

I would completely go over the fuel system. the only thing that can cause a backfire issue is a lean fuel air mixture. your diverter valve could be plugged or the pick up screen on the bottom of the tank could be partially plugged. I would probably start there.

Your Friendly Neighbourhood Journeyman mechanic

[jamison1969]

ok i will look into that, thanks jamie, any other thoughts please let me know.

[DirtDemon]

Incorrect timing can also cause a backfire, another thing you may want to check is the flywheel key. If it has sheared off, it will still have spark, but you won't get it at the right time. You could also be looking at a CDI or pickup coil problem. Another thing you may want to do is check that the air filter is clean. Also, when you say you gave the carb a good cleaning, did you take the carb COMPLETELY apart and make sure all the jets and passages are clear? You need to manually poke through the holes, spraying or soaking the carb in cleaner usually doesn't cut it. The pilot circuit is important too, you need to take the screw all the way out and clean the passage completely, compressed air helps too.

[jamison1969]

I was told that there is no way that it could have jumped timing being that it was running fine then 5 min later it wasnt but i will look into that and the other stuff you said, thank you, jamie

[DirtDemon]

You were told wrong, a flywheel key can shear off at any time and it happens just like that all the time. If the key shears, the flywheel can spin on the crank and as soon as it moves, the timing will be off. I am not saying that it is definately your problem, but I would certainly check to make sure that timing key is still intact. Good luck, I hope you can get it figured out sooner than later.

[GEARHEAD01]

yes you should eliminate that part of it even though the chance is that it can happenis small, it still can happen.

[jamison1969]

i am trying to get a manual, and then we will look into the timing and the other things, thank you all for your help, jamie

[DirtDemon]

You bet, let us know how it goes.

[GEARHEAD01]

you could also have a bad voltage regulator. the regulator holds the system at 12v. but it will decrease when it is screwing up.

[jamison1969]

Thanks everyone it was the fly wheel key, runs great again. now just need some mud or snow

[DirtDemon]

You are most welcome, I hope you find all the snow and mud you are looking for.