Gen 1 running really lean

[1967fazer]

Thanks for the reply Falcon, really am stumped on this, I've been thinking about it some more and when I think about it, the bike was running ok for a while after the rebuild and after I got the exup supposedly set up correctly, it seemed to be fine. Now its seems to be slightly down on low range grunt and this 'pinking' has arrived. So it literally has happened over the last week!
Could it down to something as simple as dodgy fuel?
Will have good check over it this weekend and make sure all correctly fastened, its possible something has worked it self loose over the last couple of hundred miles.