Thanks for the replys,thought there would be none.The damage is all round,there are undamaged patches.The main damage was at the exhaust port,not on the bridge.It is only on one side and about 1cm wide most of the damage was superficial and could be polished out with some fine sand paper 1000# but there is a 1cm streak which is about 1/2mm deep which is not viable.The straight is long and i have the JHA carb kit in so bigger pilot jet which should help with off throttle cooling and lubrication.Checked the chart and found that the needle is recomended for the 4th clip,I was running on the second.So my fault guess it got lean on the straight!.Will go up a jet size on the front/200 should do itand go to 4th klip pos to be safe.There was no sign of pre det on the crown,it was quite black.The bike was going well and keeping up with many of the 4 strokes inc the sv 650s,Guess it will be a new barrel then.Still love the NSR and it loves new parts.Thanks,Bruno