The 5speed SS50 engine that was under the motorcycle was leaking some oil from the cylinder base and behind the generator cover, so it needed to be taken apart, even though it has only done about 500km.
The problem at the cylinder base turned out to be a cylinder that wasn't flat, so it was turned on the lathe to get a flat surface for the gasket to sit against.
I thought it would also have a leaky cranckshaft oil-seal, but it was dry in the center of the generator. Next guess was the O-ring around the stator plate, when I took it off the plate, it was so dried out, that it broke instead of stretching.
So hardened it doesn't even lose its shape when broken:
when the head was off, I took some pictures of it, next to my "old-school tuned engine" this has an older type head with even bigger fins:
and more importantly, nicer ports:
Both are cylinderheads from the 5speed models, with extra and bigger fins then the 3 and 4speed models, but even then there are differences.
The other head has since been flowed to look more like the "old-school" one