Hi Dave,
Thanks for your fast response! I took the engine apart because after a recent flight, I found that the engine felt rough, felt like metal grinding, when I hand turn the prop. so I wanted to check what the cause was. I suspect it may be the bearing, but I only had no more than 20 flights and it has been running rich during this whole period and it had been running beautifully. I also gathered from the Ys spare parts list that the cylinder head and liner comes together as one part. Is that correct? Thanks again for your advice.
mck