I installed the OOR 70cc kit on mine. They deliver it without any instructions, but I did a few searches and found DIY instructions on Youtube for fourstroke engines (other models than Ace). It was pretty easy, and I've never worked on 4-stroke mopeds before.
A tip is, you will never get old head of and the new head in with the engine in it's place. The top will hit the frame, so you need to release a few of the rear engine mounts and tilt it down.
To easily unscrew the carb, you will need to get a torx-bit with a hole in the center. The screws are special torx's with a extra nob in the middle. I managed to get them out, but destriyed them and replaced with normal hex.