I was wondering if I could get a bit of background before wrenching on my brother's sportsman. Its backfiring on decel, and I'm planning to adjust the air/fuel mixture screw a bit. Could someone tell me where its located - under float bowl or in front of float bowl or... Also, what's the best way to get at the carb to do this adjustment, there's lots of plastic! I would really appreciate any assistance here, like what plastic to take off, where I can find the bolts/snaps to remove plastic, etc. Again, thanks - I've never worked with the sportsman before and would like it to go quickly so we can get out and ride!

 

Ogre Check your ETC switch before messin around with your carb that is more then likley the problem make sure it is not to tight LoL

 

ETC switch? Please elaborate.

 

Jaime, is this what you're referring to?

From mudmachine...
"Pop the cover off the throttle (The ETC Switch cover...) Inside there you will see two wires going to an electric switch... You will notice as you give it the gas, the two contacts move away from each other.. Then as you let off the gas, they come back together.. THESE two contacts should NOT touch during normal operation.. Usually, after a new machine is broke in, the cable will have to be adjusted.. But, with the cover off, you can now see what is happening as you turn the cable adjuster... As for proper specs on the "air gap".. I set mine with a 5/32 allen wrench between the contacts.."

What is the purpose of these wires anyway?

 

Ogre this switch is for frozen or broken throttle cables to shut engine off when there is no tension on the cable. At least thats what I think it is for. Usually they stall alot when the switch is out of adjustment. Backfiring could be caused by an exaust leak sucking in air on decel also hope this helps.

 

You might start with cleaning/replacing the air filter before you start getting into carb adjustments. You might be suprized what a difference a clean filter can make.

 

The wires are a switch that will shut the engine down in cae of a frozen or stuck throttle.
To adjust the gap, turn the cable adjuster located on the cable about 6 inches from the thumb throttle housing. After making those adjustments, then adjust idle at the carb.
As for backfiring, it can be an air leak in the exhaust as others have said.. It can be caused by an over lean or over rich mixture..
I'd change to a clean K&N filter, then ride it and see how it does.. if it gets worse, you are probably too lean.. if it gets better, then you were probably to rich..
You can adjust the idle mix, but you may end up needing to re-jet.. Don't waste the $$$ on a "JET KIT".. most 4 wheeler shops have an assortment of jets that can be purchased for a few dollars each... Just pull yours out, and take it with ya.. Tell the tech you think you are running lean, and youve installed a K&N.. and buy two or three different jets of various sizes....
And send all of them that you dont use to me!!.. hahahaha...
Oh, another thing to check is for a loose sparkplug.. Believe it or not, Ive seen it happen..

 

Thanks guys - I can now see how ETC switch would cause a backfire. In fact, now that I remember, it only seemed to backfire when you backed off hard from full throttle. It would seem that the ETC switch would be suspect. Also, the machine is fairly new, and as mudmachine pointed out, could be in need of readjustment. I'll look at this first.

 

My gosh, thanks so much for the great advice. I pulled of the cover to the switch, started her up, and watched as the ETC switch went in and out as I flicked the throttle. Indeed, this was the problem. This is certainly an interesting safety measure. Anyway, the sportsman is back in all its glory.