Hi guys--------- First, you only need to remove one clip in order that the piston can be removed ( Remember to put the piston at TDC and pack plenty of cloth in the crankcase mouth.)........................Here are two similar types of grooves in the piston skirt that allow you access to the retaining circlip..

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--------------------------------- using a small flat-bladed electrical screwdriver you simply insert it into the groove and under the clip.......By simple leverage the circlip can be removed...........Try to avoid the types with a small head on or with the ends curled around as they could break off with age...........