Drive side oil seal.

Rotor should pull off by hand or a light puller as its on a parallel shaft, the engine sprocket is on a taper and a much tougher job. So for the engine sprocket you need a heavily built puller with legs long enough to get behind it, even then you may need to use a propane torch on the sprocket followed by a stout hit with a hammer on the puller before it breaks the taper grip. The seal is in the crankcase and there is no room to pry it out, drill 2 small holes in the seal and then screw 2 self tappers into these holes and then pull on the self tapper. Try and get a seal with an outer rubber surface for a higher chance of it sealing on the OD.