Not sure what the problem is here but I drive a Rieju MRT 50cc with an AM6 engine and it does about 31 MPH stock. So there's a rattle like a spinning noise hard to describe, but it runs fine otherwise but it vibrates a lot at high rpm and rattles that begins near max speed when revving about 10-14k rpm or something not only when driving also in neutral but mostly noticeable when driving. It has about 10k km now and I think the engine hasn't been opened up before, and I'm thinking of opening it but don't quite have time rn but maybe before next year. So the rattle is definitely in the inside of the engine not fully sure where in the engine it comes from but it bothers me a lot. Linked a video of it in second gear but gear nor clutch makes no difference. https://youtube.com/shorts/ATZWItbHRcM?feature=share