u/BOC16

Cr125 2003, Brand new cylinder barrel and piston all measured within spec. Had to pull apart as didn’t realise I didn’t need a headgasket with the VHM head. Upon taking the cylinder head off I noticed the barrel has very light scoring on the walls can only just make it out with a finger nail.

The bike has only been started once and run for around 4 minutes and then shut off. Any ideas what caused it?