It wouldn't worry me if it had done 18,000, it is still a good buy at the price. The engines are good for 100,000 easily. Who was it that lifted the head and looked at the barrel after 70,000 odd and found the original honing marks were still present and no wear whatsoever had taken place. People worry too much - my Morini 350, not exactly known for reliability or longevity, covered 187,000 trouble free miles before I sold it. It went on after that to clock up 250,000 and is still going strong and is known in the Riders Club. Change the oil and filters regularly and you are more than half way there.