Pull the HS needle and check flow. You are on the LS needle until 3/4 throttle so good idle and transition may not show a lean condition once on the High Speed.
Only idea I would come up with to get that drive washer off would be to stick the engine in a bag and leave it in the freezer overnight, then while still cold heat the washer as quickly as possible. The hot glycol dunk may help if this does not work as it would tend to loosen any dried lube that may be locking it together.
Personally I modded a battery terminal puller like the one in the pic and have used this to remove drive washers on everything up to Saito 125's and YS 120's, although a bit of creative work is required when the threaded portion gets longer.
This will usually break them loose and even tension while heating can have them snap if difficult.