Motorcycle Repair: yamaha 1981 400 special 11 idle problem, lean condition, definatly

Question
This bike runs good from 1200 rpms and up it seems. I have cleaned the carbs as good as I thought I could.  I have been told that they have caps that need drilled out over mixture screws and jets on the carb I have not messed with any of those.  If I try to turn the idle screw up it will idle then break up and rev up to 4 or 5 thous rpms and I cant get it to idle.  I have adjusted the valves.  I have not had the carbs sync.  Someone said I should take the caps off the carb and clean in there.  Any suggestions please.
thanks

Answer
Have the carbs been seperated from each other?  If so, then u have a vaccum issue from unsynced carbs.  Otherwise your jets may b slightly clogged, if u decide to clean them b VERY careful not to accidently "bore" them with whatever u use 2 clean them.  You can remove your caps to clean in there, but DO NOT turn any screws under the caps, however I've never heard of dirt in these chambers causing a prob unless extremely excessive.  DO NOT drill out anything!  Your prob sounds vaccum to me, or at the very least your bike is rich since it will idle.  Tell me this, Does it pop and spit from the exhaust when u throttle it up?  If so, then u r most definatly dealing with clogged jets causing a "lean" condition.