Hello, I just picked up a 98 Mojave 250 for $900. It has a K&N air filter, a Cobra exhaust, and a carborator that was put in new a couple years ago with a dynojet kit. The sticker on the side of the bike says dynojet 1, so I am assuming it is a stage one jet kit. Anyways, the kid I bought it from told me that he always rode with the choke about 75% on, and he showed me where to put it. He said I probobly just had to mess with the idle screw, so I did. Origionally, the quad would stall out as soon as you pushed the choke off, so i turned the idle screw way up, and was able to run the quad with the choke off. I assume that the idle screw is ONLY idle, not the air/fuel mixture screw right? Well anyways, so I went out for a ride, we were on the powerlines, so lots of hills, rocks, some straight aways, so I wash pushing pretty hard. After about 20 minutes of riding, it started to cut out on me when I gave it throttle, almost like it was running out of gas, or like the jet in the carb was clogged or something. It would not go, just wanted to die. I pushed the choke to somewhere around 50 to 75% on. Usually, an engine would stall out immediatley if it was hot already, and you put the choke on, it would need more air, but in this case, it let me ride for longer. I was able to ride for about another 20 minutes like this with no problems, again, pretty hard riding. Then it started doing the same thing so I turned the choke back off and got another 20 minutes of riding with no problems. we got back to the house and took a cig / water break for about 10 minutes. We tried to go back out, but when i got into the trails it started to cut out again. This time no matter what i did with the choke, it did not want to go fast.

So, what can i do? What do you think it is? do you think its the jet kit doing it? Should I buy the stock jet and put it in? Is there another screw on the carb i can mess with? Where is it? I just found the big screw the is vertical and moves the throttle thing up and down to adjust the idle. But i also didnt take any plastics off or anything. What can i do? Thank you!!

 

put some carb cleaner in your gas and let it idle for awhile, then try to tool it. you might want to clean/change your air filter to.

 

Okay, here's another thread out of the dust-bin..

In case you're still having idle problems:

The idle mixture screw is on the underside of the carb near the engine-side exit. If it's plugged, you'll have to remove the plug by drilling it and using a sheet metal screw to extract it. Be careful, the screw slot is right behind the plug. Gently screw in this screw until lightly seated, then back out 2-turns to about 2.5 or until the idle smooths out. Take some of those turns off the speed screw and check it again.

In the attachment, the screw is to the right of the float bowl area. It's down the "hole", the plug has been removed.

 

ya.. theres GOTTA GOTTA GOTTA be a mix screw on a carb.. 2 or 4 stroke..

note the positing of the slot, then with your tiny little flat screwstick, turn the screw in til it stops and cont the revolutions... should be about at least 2.5 or so.

take it out and inspect the tip for erosion or being bent, also inspect the o-ring in there and the tiny *** little spring that resides in there..

if the screw looks nice, shove it all back in there and twist it in til it stops. then, turn it out 2.5 turns, (or where ever it was if it was over 2.5 turns) start the beast.. and see how it idles..

if it was less than 2 or so turns in, give it about a half turn and go from there. there should be no real rich idle condition indicated by smoking and nasty running..

you might need 3-3.5 turns to get it to settle down.

the choke creates a rich condition. if the carb is naturally jetted or tuned too lean, choking the hell out of it is the only salvation.

play with it and keep us posted! welcome to KF!!!