i currently own and have just bought a gpx-4 pro. it has a rossi pixi black and a centax 3 shoe clutch. i have tuned it well and i have turned the little set screw anti-clockwise to make it change into 2nd quicker but it still wouldn't change. i took apart the clutch and loosened the little spring alot and yet again it still wont change. and yes i am sure i have a 2 speed in it lol.