..i would not use any standard gy6 engine parts...
..when ordering parts, make sure they are stated to be compatible with the A50...
..i orderd a 1500 contra spring for a gy6 50...the diameter was too small, but it fits my junker Marshin that has a 10" rear tire...
..however, most cvt parts of all the kymco 50s will interchange dimensionally...