The teflon tape I used disintegrated pretty quickly, so I gave up on it.
For the tap to the tank, I use a doughty washer (copper with bonded black material inside) and Loctite 577 thread sealant. I think either would probably do. The operative word is probably. Fuel leak above hot motor, not a good thing. Ask me how I know.
For the tail to the tap, a touch of the same sealant seems to work for me.
Maybe your kickstart lever has some lateral movement on the shaft, and moving it in or out might make room for the cotter pin.