I have a 2001 4x4 Big Bear. Up to this time it has never given me a seconds problems. I use it gently for hunting and keep it washed and in the garage so it is well taken care of. I used fuel stabilizer over the winter.

I was riding it after it sitting up for a couple of months and it started backfiring and bucking and finally quit on me. I got it started and the same thing happened. Then it started and ran OK. I changed the plug and it ran fine the next 10 or 15 times I took it to the woods. I was using it about two trips a week. Then I didn't go for two weeks and as soon as I cranked it in the garage it started popping and bucking and would not stay running. It would idle but did not want to take throttle.

I pulled the carb, it looked clean, but I cleaned and blew out all the jets and passages. I drained the gas tank, removed the shutoff valve and blew it out. The little filter was clean plus I added an inline filter, and checked the tank for drbris. It looked good and the tank vent and all other vents were checked. I put it back together and same problem.
The choke tube seems to work normal. It looks as if it just opens or plugs a passage, is that correct?
I wonder if it could be a spark problem even though it acts like fuel.
As a side note, the plug was black and dry when removed. There is no "flooded gas smell".

I will take all help and hints before i have to take it to a repair shop and put myself at their mercy. I have a lifetime of mechanical experience but not on ATV's and I have never seen a carb quite like this one. I am lost on this one. Thanks

 

Make sure a mouse hasn't built a nest on the air filter. Also foam air filters can break down and cause problems just like you mention. I have seen it happen on a '01 banshee last year. Finally, I have tried staybil fuel stabilizer twice and have only had problems with it. Loss of power and acting like there is water in the gas (same problems you have) are my complaints with it. You might try draining all of the gas and sitting it aside and try fresh gas. Before you do anything, put a new plug in it.

Please let us know what you find. A lot of newcomers ask questions and never post back up. This keeps a lot of members that have good ideas from wasting their time replying. Welcome to the forum. There is a lot of good information here.

 

A couple of things I'll mention is the parking brake rev limiter and the carb joint( intake boot). I have seen those parking brake rev limiters cause that same trouble. Make sure every thing is in order and not sticking on you. The switch, located in your right hand brake perch, could be sticking or the wires loose. The carb joint, between your carb and engine could be leaking,(sucking air) a way to test this is to spray around the joint with stating fluid with the machine idling. If it revs up from the starting fluid you can figure the joint is bad. I have seen those go bad from the backfiring and popping from the rev limiter. Let us know what you find out with it. And by the way welcome to the forum.

 

One other thing I'll mention is the in line filter. I have ran those small round cone shaped ones for years untill this year. I was having carb troubles from the machine sitting for awhile so I cleaned every thing out and it ran good for awhile. Then it started the same thing again. When I took it apart I found little pieces of brass out of the filter stopping up my pilot jet. I don't know if I just got a bad one or what but I quit using that kind.

 

Thanks for all the ideas. I HAVE MY FINGERS CROSSED but it appears to be fixed. I only did two extra things, actually three. I cleaned the spark plug but it looked fine and was new. I washed the foam filter even though it was pretty clean and not even discolored. I had apprehension about messing with the air/fuel screw but I counted the turns, removed it, sprayed everything with carb cleaner and counted the turns to reinstall it.

I left the air box off and gave it about half choke and it fired right up and idled fine. I gave it throttle and again it was fine. I installed everything and road it up and down the street and around my yard. So far no problems.

It is almost scary that I don't have a sure idea of what fixed it. I do know the boot on the front of the carb was not real tight, I could turn the clamp. Nothing else I checked including all the vent lines were open. I did find out when I accidently put my hand over the air box intake, that it will stop right now without air. So the foam filter may have had something to do with it.
I will be able to give it a good test after Thanksgiving and I will report back. If it happens again I may be thinking about spark instead of fuel.

I need to buy a shop manual!!

 

Just as a follow up. The Big Bear is running great. I had it in the woods today and took it into some rough areas and up some big hills. It never sputtered or missed a beat.
It was just below freezing and after sitting outside all night it started right up and idled fine.

I still am not sure exactly what fixed it, possibly some super tiny trash in a jet or sucking air from the loose front boot.

Again thanks for the help and ideas.[img]i/expressions/face-icon-small-happy.gif[/img]

 

I had the same issue, and found that the gas line overflow tube on teh cap was kinked, so no air was replacing the gas used in the tank..