Thank you Pleiades & UKbri- I sort of suspected it had bought it...when I get the new chain- I will check all parts etc & report back...at least it sounds straight forward to replace...once I have the mortgage in place!
        
 
         I will also check the sprocket teeth at front & rear stock is 
        
15 & 46????- it typically showed 10% over the actual speed- maybe the previous owner had altered the gearing.
         
        
 The hunt will start for a chain guard also!!
         
        
 I'm editing a film to be released - it does include an XT660z- here's a small sequence...I hope you enjoy it! 
        
https://www.youtube.com/watch?v=s2NWB9yGv6A
         (if you cant see it...let me know)
         
        
 Thanks again!
         
        
 Rod