I am having problems setting my carb for idle, to begin I have a trail boss 250 with a Mikuni 34. when I try to start the quad I have to half choke it once it starts I take the choke off immediately, feather the throttle a bit and it wants to die so i click the choke on and off really fast to bring the idle back up I need to do this 4 or 5 times before the quad will stay running. if i turn the quad off and let it sit for about 2 minutes i need to half choke it to get it going again. yesterday I pulled the carb apart and made sure it was clean put it all back togather and still the same thing is happening I played with the air screw but it didnt seem to be doing anything. I have great compression (143psi) and no air leaks anywhere that i can find. could it be possible that the air duct for the air screw have something in it causing me not to be able to adjust? I turned it all the way in started with 1 turn out went to 2 turns out and back all the way in with no differences. Thanks.
I did a search but couldn`t find anything with my symptoms.

 

it sounds like lack of fuel for sure. is the flaot set right so it's getting plenty of fuel and you sure the starter circuit is completely clean as well as the jets? if you have to choke it to start it then it needs more gas for sure.

 

I took all the jets out and run a torch tip file through them. I didn`t measure the hight in the float bowl but bent the float arm so that it was flat (able to retain more fuel in the bowl) and took carb cleaner spray to every passage i could find all seemed to be clear. Think if i was to move the C-clip on the needle down 1 it would help its set on the middle setting now.

 

Mine acted like that ,it turned out to be the throttle etc switch needed a adjustment.

YouTube - Polaris ATV Maintenance & Repair Tips : Polaris ATV Thumb Throttle Maintenance Tips

 

TLC do you mean the switch inside the thumb lever?

 

unless you did some mods where it needs more then a stock flow of gas, you shouldn't need to move the clip any to fix it. is the air/fuel screw needle damaged? you said there is no changes by adjusting it.

 

yes that is what he means.

 

I didnt take it out to see, I have another carb on the bench think i should switch them and see if that helps? yes no change while adjusting

 

I`ll try both suggestions hopefully something works. Only mod is a 155 main jet havent tried it yet but thinking I`ll have to drop to a 150 145 is stock

 

you did clean the pilot jet?