Hello all
I have strange problem, which I've been struggling for some time now.
The engine is YX150 but with KLX110 cylinder, piston and head. I got it from some pitbike racing team, they told me KLX110 parts were for reliability.
A year later maybe the engine developed ringing knock, which sounds like piston related for me. Hotter the engine goes, louder goes the knock.
In this autumn I took it apart and found nothing suspicious. No play on conrod or wrist pin, nothing banging together... Perfectly normal engine. Maybe a bit worn wristpin, which I replaced. After putting it back together, the knock is still there.
Video here:
https://goo.gl/photos/kLU9ut3BWBJ9C6F58