I've made this small 1 cylinder engine fidget toy. It contains the following pieces and should be assembled in the following order:
I recommend using the print file that I've made as I've tried many different things where different components fail. I've scaled the original STEP files up by 200%, but it is possible to scale it up or down for your liking.
Let me know you you'd like it in a V2 or inline 2 engine. I can quickly modify the files.