Gents,

A picture of my 30 years old ENYA 60 4 C engine.
I did make the picture when I did repair the thread of the glowplug.

This Is all I can show you because, why should I remove the valves?

The material of the valve is harder than the seat. Even a very little scratch on the valve and in my opion, it is end of story. You can lap a seat but not a valve.
The rocker will hit the stem not exactly in the centre and it is often done this way (motorbikes) to let rotate the valve.

Of course I cannot compare the power with the other engines on the field, but he can pull the Orion, nearly 10 pounds, 70 " span.

Cees