Chased similar issue with a 400EX, thought it was valve adjustment. Though the valve adjustment was needed, it ended up being a fuel issue. Lean on idle. What you think is an air screw is actually a fuel screw.
Maintenance was so lacking,, it came to me needing the whole axle carrier needing replacement because the bearings worn so bad the axle wore into the carrier.
Maintenance was so lacking,, it came to me needing the whole axle carrier needing replacement because the bearings worn so bad the axle wore into the carrier.