Abstract: A fuel supply assembly for a two-stroke crankcase scavenged combustion engine that is operated with layered scavenging is presented. The assembly includes a housing and a first and second parallel channels extending through the housing. The first channel is for a fuel/air mixture and the second channel is for auxiliary air. The assembly also includes a partition wall extending in a plane between the first and second channels and arranged upstream and downstream of at least one butterfly valve. The assembly also includes a protruding section which extends across the butterfly along the axis of rotation at least on the downstream side of the butterfly. The housing includes fuel-conveying idling ducts that open in the first channel in the region where the butterfly valve, sealing member on the partition wall, substantially contacting the protruding section at least on the downstream side of the butterfly.