What effect does a missing mixture screw oring make? The spring would stop the screw backing out and washer is to protect the oring.
Cunning Honda engineers put an oring there for a reason. Any practical experience by anyone on a missing oring.
It stops air being sucked in past the threads of the screw…last thing you need at idle is too much air being drawn into a carbie at idle causing a lean condition…screws up the bottom end performance and idling becomes poor.
Smithy.