TOPIC:

Thanks everyone for the help. These are a few pics Zed Parts sent me. the other pics are all over the place as I completly lost interest in the bike. Were going to take the head of again me thinks and give it a good check over. I have a video at work of the bike being revved and you can here the tapping. will post tommorow night.
Many thanks again.
Neil.

Looking at the first picture it's apparent the cam chain is rusty. The 2nd and 3rd picture of the cam gears shows some nasty uneven wear on the cam sprockets. I'd guess the cam chain links are (partially) seized, which would account for the "rattle" because the cam chain is being "forced" throughout it's path.

Supplement: I'd advise to NOT run the engine until the cam chain has been replaced! Doing so could likely ruin the otherwise usable Plastic tensioner sprocket. Not to mention the rust debris that'll end up in your lubrication system

I confirm scotch, my exact thoughts when I saw it. Even looking at the crankcase I thought where those dark brown rusty like areas come from, must be rust inside the case. And the teeth look quite worn, despite the nylon sprocket still usable.

this is a vid of the bike.

sorry hasn't worked again.