Having discovered my piston and barrel had suffered from a lack of lubrication , I had to get a new piston and ,as i thought have the barrel replated . Having taken the offending items to a motorcycle engineers , I was informed it was a cast bore and was reborable .How ever when further investigations by the engineers to locate the correct oversize piston were undertaken ,my engine and frame no.. indicate that that model was made in 1991 MKII and should definately be plated ,although the barrel is factory fitted . Can anyone shed any light on this pedictament . Plate or rebore ?

They are cast not plated. You can get oversized pistons and rings from LT, I think they even do 1mm oversize genuine honda pistons. The MK11's are definitely not plated

Thanks for that re assurance. It has been rebored to 66.5mm and fitted with a patent TRX 250 quad piston. It's now run in and runing on premix , cos the autolube just seems to ooze rather than actually pump anything. It is running better than ever starts second time when left over night and first time when its been upside down in a rut, I hate ruts . CRM rock !!!