something wrong with the idle screw?/

hi guys, when my bike last came out of the garage it had a few starting problems... i found out that the idle screw was wound too far out and when i wound it in to where it would idle it started absolutel spot on! only thing is about a month on i had more starting problems and cured it by winding the screw in a bit more. i'm now having more starting (and idling) problems and want to know if i should keep winding this idle screw in as it has worked the last couple of times! do i have an underlying fault or does the idle screw simply un screw itself with the vibration?? also when i get the back wheel up under braking (over 6 inches) the engine normally dies/stalls when it lands back down! very embarrassing when i'm showing off up to traffic lights! does this have anything to do with the original problem? my bike is an '03 501 FE.
regards, ben

never changed the needle or atomiser! was tinking about going down the keihin fcr route... maybe i'll do it sooner than i thought! will be calling you very soon taffy!! also when you say tappets taffy do you mean valve clearances??
regards, ben