What bike is it...or rather what model?

Well I am stumped, after a good listening to the clonking it seems to be coming from the front exhaust rocker, now I am not sure if there is anything up there that would cause this, is it possible a faulty hydraulic tappet may cause a noise at the top end or could it be a worn rocker shaft? the primary and compensator seem OK.
Anyway I am going to pull the top end and was after some recommendations for gaskets and what to look out for when I am in there.
It's a good job I quite enjoy working on the bike as I spend more time doing that than riding it

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