Promised update
Received this week the new piston and gasket from Poland.
Gave the cylinder another caustic soda bad and some honing.
Mounting the new piston was a bit of a crime, no space for putting the circlips in an easy way, anyway managed to get them in.
After putting everything back the big moment, not starting and no compression
After cracking my brain I suddenly found this part in the belly pan, chain guide I never seen before. Must have felt out when I removed the cylinder head
Stupid mistake, after disassembling and trying to put everything back together the chain felt of the sprocket from the crankshaft, great...
Anyway, some hours later the Kymco is starting en running pretty good.