Hello all

i have a mystery noise on my mid 70s honda supercub 70cc. The motor may have been changed to a 100cc. Anyways you can hear the noise in this video. Its more pronounced as the rpms go up and is really noticeable when i hit or release the throttle. The best wayni can describe it is eee eeeee eeee. With the bike onnthe stand, it doesnt make the noise. Only riding. Any ideas? I cant find a similar noise in any videos.