This is a great forum! I am new to the ATV world. Just picked up a '87 bigbear 4x4 for ice fishing use. My problem is I can't seem to get the idle speed to drop down enough no matter how far I turn the idle screw down. I have cleaned the filter and tightened the intake clamps and that helped somewhat. It idles highest when started cold and does somewhat drop down when it warms up but not enough. To shift into gear I have to pull out the choke to get the RPMs to drop down. I have also checked the throttle cable thinking it was somehow giving some gas but it isn't the problem. This thing starts and runs great otherwise. It will start without the choke even yesturday when it was only 10degress out and had been sitting for 2 days. The guy that had it before me kept it in a heated shop and it didn't seem to have this problem. Any ideas

 

If its gonna start at 10 degrees and no choke, then its probably adjusted too rich.
Id say the uncontrollable reving, is due to a vacumn leak. A motor cant rev without air, look over the rubber intake, theres a missing gasket, or rip, or hole, or loose clamp, or bolts.

 

Thats what I kinda thought about it starting when it is so cold, it must be rich. Like I posted in first reply I did tighten up clamps and airbox lid and the did help quite abit. But there is still something else and its got to be the fuel mix but I tried adjusting that screw on the bottom of the carb but it is a MF to get a screwdriver on! I think I am going to have to try and loosen carb and tilt so I can get at that screw. Anyone know which direction to lean it up and how much should I start with. And does this sound like the cause? Thanks.

 

If you can fit your fingers in there, get a #4 flat bit from sears or home dump, and that should do the mixture screw. There shouldnt be much resistance on the screw. About 2 turns out from lightly seated, is a good place to start.
Heres a good article on adjusting carbs, let us know how it goes.
jetting
Going in is leaner, on that mixture screw.

 

Either your air/fuel mixture screw is too rich or most likely your throttle cable is stuck or too tight. It could also be something stuck in your carb, not allowing the slide to return to bottom, but that's unlikely compared to the first two suggestions.

 

yep

 

Honda Buster,
Thanks for the tips. I also think this thing must be running rich because it starts so well in the cold! I tried to adjust the Pilot screw but that thing ain't turning! I tilted the carb to get a screw driver on it and the head/slot has been messed up, so no way to get it to turn. Anyone have any suggestings as to how to get the pilot screw out now?

 

Well guys I got some good news and some bad news! Bad news is I think that pilot jet is staying right where it is at! I bought a extractor and tried to drill a hole in the bottom of the jet and use the extractor to back it out but the jet is made of(brass?) soft metal and the extractor won't bite so like I said pilot jet ain't gonna turn. BUT while I had carb partially down I took that black side cover off to see just exactly how the Idle screw works. Once I got the cover off I could see that the throttle seemed like it was advanced some and the there should be more adjustment with that idle screw so I started messing with the cables while snapping the throttle and the thing snapped back into place! I don't know what it was something must have been either stuck in the carb or stuck inside that splitter where the primary thumb cable cable comes into the splitter box for the dual cables because I took the cover off the thumb throttle and that wasn't it. Now I can adjust the throttle all the way down till the motor dies. Hope it still starts good! Thanks for your help guys!

 

The pilot jet is inside the float bowl, next to the main jet. I think you mean the mixture screw is buggered up.
Some how, youre gonna have to get it out, its probably jammed into the seat at the bottom of the screw...but anyway, this is the fine tune for the idle circuit, and its gonna need to be about 2 turns out from lightly seated. The last guy buggered it up, and to compensate he turned up the idle so high, that the midrange was his idle circuit. Its not ever gonna run right til that screw is replaced.
It is made of brass, and has a needle point on the end of it. If the extractor wont bite, try pushing inward on it, while turning ccw. That extractor should have a left hand helix. and turning it ccw will make it bite. If you still cant get it out...either a machine shop( try the local trade school, when I was going to school, people brought all kinds of things in to be fixed...we didnt charge anything, because we enjoyed learning on someone elses parts), or buy a new/used carb.
Bottom line...that screw has to get fixed, or it wont run correctly.