thanks for the replys guys,i did mean to ask what you guys thought caused the damage,the piston is only gouged on that one point.not really other signs of it seizing on the piston,that would make sense that it was caused by the main seals going..id prob be as well as to get the barrel honed? ,measured and buy another piston...just greaves me cos this one still looks brand new!except for the gauge and hotspot on the one exhaust side,the rings still look like new honestly only had the thing running for prob less than 30mins.. ,as i have no acurate gauges to measure the bore myself, can i get an idea from the old piston size? which reads std575ps TD in the centre and on the inlet side reads j4oc2