"The usual 61FX air leak"???

Never had it and never heard of it. Every 61FX I ever had and ever knew of ran perfectly right out of the box. We're talking approx 25 61FX's over the past few years at two clubs. Not one had any air leaks or needle valve problems - period.

The symptoms you speak of sound like you've perhpaps peeled the liner from too many previous lean runs. It can happen. Pull the head, wipe out the inside of the liner and take a look.