28ml PHBH four stroking

I recently had an RT195 kit fitted to my Li Special. It has a brand new Dell’Orto PHBH 28ml carb which is proving virtually impossible to set up for a non-spluttery ride. My friend, a motorcyclist and scooter rider for many years has tried many jetting set ups but it has got him beat. The scooter goes well, but once you ease back on the throttle the 4 stroking kicks in. Under load it’s fine, but ease off to steady the speed and that’s when the issue starts. Would a dyno session possibly cure it?
The current set up is 50 pilot, 126 main, X13 needle second clip from the top, 264 atomiser. I’m not using the air box but there’s a foam air filter fitted directly on the carb.
Any advice would be gratefully appreciated.
The current set up is 50 pilot, 126 main, X13 needle second clip from the top, 264 atomiser. I’m not using the air box but there’s a foam air filter fitted directly on the carb.
Any advice would be gratefully appreciated.