I purchased a Bayou 250 in January of this year. It has been back into the shop three times now because it consistently stalls on idle, even when warm. The first time they adjusted the carborator. The second time, they found a crimped fuel line. That corrected the problem for a week or so. Now it's doing it again, only worst. Last night while riding it (it was 65 degrees here) and when I let off the gas to go around a corner, it stalled two different times and I almost went over the handle bars one time because it stopped so quickly. No matter how long I warm it up or ride it, it still stalls on idle. I use good gas, it is stored covered, I am not riding it through a lot of mud or water.

Any thoughts?

Thanks.

Michelle

 

Assuming the idle speed isnt too low, it could be a low or high float level, dirty air filter( was it cleaned and reoiled?),partially plugged idle jet(was it replaced with a new one?), misadjusted mixture screw( should be about 2.5 turns out from seated).
Does it restart right away...and then idle ok? If its just sitting there idleing....and you shake the quad, does that make it die?

 

>Assuming the idle speed isnt too low,

That they adjusted the first time.


>it could be a low or high float level, dirty air filter( was it cleaned and >reoiled?),partially plugged idle jet(was it replaced with a new one?), misadjusted >mixture screw( should be about 2.5 turns out from seated).

I'll ask to be sure that they checked these things. It is not the air filter, that I checked.

It is odd that there was a crimped fuel line, that was fixed, it ran fine for a bit over a week, now is running bad again.

>Does it restart right away...and then idle ok?

Sometimes it starts again hard. It never idles okay, it stalls if the choke isn't on, even if it is warm.

>If its just sitting there idleing....and you shake the quad, does that make it die?

Haven't tried that, but given that it stalls just sitting there ...

 

When you say it stalls when the choke isnt on...makes me think its a plugged pilot jet, aka the idle jet. Id replace it with the next size bigger jet. The hole in the center of the jet, is incredibly small, and easily plugs up . Its so small, that its difficult to clear it, so just have a new one put in, and have it one size bigger than stock, and itll start and run better, then have the mixture screw readjusted.

 

>When you say it stalls when the choke isnt on...makes me think its a plugged
>pilot jet, aka the idle jet. Id replace it with the next size bigger jet. The hole in
>the center of the jet, is incredibly small, and easily plugs up . Its so small, that its
>difficult to clear it, so just have a new one put in, and have it one size bigger than
>stock, and itll start and run better, then have the mixture screw readjusted.

I ran your suggestions by the mechanic and he said they've checked all those things. I'll post what the outcome is.

Do "bum" ATVs sometimes just happen?

 

Id still replace the pilot jet, its easy to change and is only 5 or so dollars, plus haveing a bigger idle jet will make it easier on cold starts.
The bayou is a very good, dependable machine..I think its easier to find bum mechanics.

 

They said the spark plug was fouled (again!) so they are going to put a "hotter" plug in. They said they are going to adjust it so it's running leaner. They said I am not letting it warm up enough prior to riding it. How long should I let it run prior to starting to ride it?

 

You can drive it almost immeatitly. Just blip the throttle,in neutral and when the hesitation is gone, its good to go. Move the choke to off, as soon as the motor will let you. If it stumbles, or pops back thru the carb,(when giving it gas) its still cold.
Is the mechanic able to duplicate the issues? When he is done...can you ask him to show you how to warm it up....and when its time to drive off? When he is done...are the issues fixed, before you take it home? Can you test drive it where he is?

 

I have a 2001 Bayou 300 2X4, that is having similar problems. I put in an overhaul kit, but failed to check the number of turns on the pilot screw. I set the new pilot screw at 1.5 turns out. Now The motor starts quick if you don't touch the choke or throttle. If you touch either, it floods and is near impossible to start. After warm-up it idles fine, but once under load, it stalls about every 10 seconds. Fuel flow is good and air filter is new. How many turns out is standard for the pilot screw? Would that be a possible solution to my trouble, or do you have other suggetions? Thanks, Robert

 

1.5 turns probably isnt enough. Heres a good article on adjusting the mixture screw. http://www.motorcyclecruiser.c...arburetion/index.html

And it says to
"Start by bringing the engine up to operating temperature. Open the throttle slightly. Does the engine pick up speed smoothly? If it doesn't, the fuel-mixture screw may be out of adjustment or the pilot jet may be either too small or too large. To determine the pilot screw setting, adjust the idle-speed screw so that the engine is idling slightly fast, somewhere between 10 and 20 percent above the recommended idle speed. Using either the manufacturer's or the jet kit's recommended pilot screw setting as a starting point, turn the fuel screw left or right between 1/4 and 1/2 of a turn. Select the screw position where the engine speed increase is the greatest. Readjust the idle speed to the correct level.

Next, take the bike for a ride, preferably on a relatively quiet, straight section of road. Using your throttle index, run the bike at 1/4 throttle. If the pilot jetting is correct, the engine should run smoothly, and it should be easy to maintain a constant speed without varying the throttle position. If the bike surges or hunts, the pilot jet is probably too small (lean). Other indications that the pilot circuit is lean are popping or spitting through the carburetor when the throttle is opened and popping or backfiring through the exhaust when the throttle is shut. If the pilot circuit is rich, the engine will have a rough idle or may not return to idle without "blipping" the throttle. You may also notice a distinct smell of raw fuel and some eye irritation from the exhaust."

Also check to be sure the o ring at the end of the mixture screw is there...and not deformed.