Check for vacuum leaks coming from the bush area the throttle plate spindle in the Hitachi [SU] body. If there is not enough air going over the bridge then no fuel [insufficent amount] will be drawn out of the jet.
Also worth checking the throttle plate as well as they flog out on there sides from years of service.
Can you confirm the correct profile needles are installed to match the engine CC's and Camshaft specs