From the looks of the intake valve and cylinder walls, there is a high amount of dirt ingestion causing excessive wear The intake valve covered in burnt oil suggest that it is pulling in oil from the breather and burning it. The intake valve seat and valve face are showing wear which could result in the valve not seating properly and therefore not sealing against the seat. The exhaust valve looks to be sitting too high in the seat with uneven valve face to seat contact area, which could indicate either the exhaust valve is bent or the seat isn't sitting flush with the valve.