Chainsaw Repair

Kev, are you saying the metering side carb cover is drilled? Kinda odd, but if that's the case, that would tend to mess with the carb mixture somewhat.  I.e stihl Intelicarb system.  Doubt that's the real issue but it may make the carb adjustment fussy.  Make sure the enrichment system us indeed defeated, short of that maybe case gasket or seals are bad.  Loose cylinder bolts??   Adam