xr250L carb problem

xr250L carb problem
I've got a '91 xr250L model w\a supertrapp.. used strictly offroad..
problem is that the engine 'hunts' .. that is, it won't idle evenly it will start low (like when the throttle is blipped) then climb back up to a relatively high rpm.. if I back the idle speed and it won't accelerate well.. it'll bog then catchup.. it gets to its high rpm then the rpm will vary .. seems like an air leak .. I did spray some wd40 around the carb/manifold union thinking if it were sucked in it would rev the motor. but, i realize now that i missed the engine side of the manifold

prev.owner put a larger main in it but, that clearly isn't an issue now .. there is a limiter cap on the idle air screw.. heard it was reccd. to burn it off and get full adjustment on the screw.. not done yet.. Any thoughts appreciated..

fencr@hotmail.com
marc

I pulled the carb friday night.. found that the cap on the idle screw was spinning and the screw was stuck in place ( at first i thought the screw was stripped) ..then i actually sheared off one side of the screw slot trying to turn it.. i spritzed it down with carb cleaner and put some gasket sealant between the mainifold and the carb and that helped the wandering idle speed some.. it ran well over the weekend but, i think i'll put the R model exhaust header i bought on it to get more flow.. my friend thinks it isn't breathing well enough.. it climbs like a goat and pulls well but, off idle isn't too impressive.. i'm not expecting a 2stroke jump but, a cleaner/lower idle speed and a bit more pop would be what i'm after..

i did pick up a larger idle jet but haven't installed it.. i'll need to get another needle to make that happen .. i grabbed a 42 'cause that's what the shop had but, i wanted the 40 just to go up one step..

I wouldn't mind finding a carb for the R model bike to put on this L.. but, it isn't a real priority.. thanks to you both for your thoughts.. it helps to bounce the ideas around..

You're right i am referring to the pilot jet .. and i see now that i was saying idle screw when i meant the mixture screw..
but, i think what is somewhat lost here is that i am starting from an L model bike with a carb that was factory jetted to comply with emissions rules for the street.. it was a dual sport not an XR-R model.. also it will probably benefit from a good thorough cleaning if i could get all the openings open (like getting the mixture screw out) .. i've done a couple partial cleanings but, something has always held me back from stripping it completely.. most recently its that the mix screw won't come out without a fight.. so i'll order a new one and convince the old one its time to go..
as to the trapp opening up the middle and top end more and robbing from the bottom .. ok .. i would have thought it would have increased power across the whole band since it was less restrictive than stock and more flow means more fuel burnt etc .. of course when you change the exhaust you need to match or optimize your mix setting to match.. and i don't know how well that was done until i get the screw to move..
so .. there are a couple things i can do now that may improve the situation before overboring etc..
but i'll ask around about what i should be expecting from that trapp.. thank you