have you checked air jets arn`t blocked, air hoses fited correctly.
When i was sorting jets when i had much to big mains in air screw did nothing. but if plugs arn`t to bad could be the air deliverey slighly blocked.
Have you taken the air srews out and checked for wear .
You could also check oil pump adjustment.
I`d take carbs off first clean right out check for blockages,wear.