You probably are too lean on the idle needle. The idle needle provides at least half of the fuel that the engine needs at full throttle.
Do not go leaner than factory settings. If that does not work well, check the fuel line right up to the carb for leaks. Also check the crankcase to carb pump pulse line for leaks.
I quote from the manual:
Carburetor adjustment:
Basic setting: adjusting needle ( L ) for low revolutions range 1turn and 45 min
adjusting needle ( H ) for high revolutions range 1 turn and 10 min
(the values are derived from the position of clock-hands)
The new engine comes adjusted to the basic setting. This setting
should be kept during running the engine in!