MY guess would be chasis knocking rather than engine but as its constant but what would I know.

I've tried holding the handle bars and wiggling the front wheel to get any play and seems ok. As much as I can check in the dark and wet moving the rear swingarm and rear wheel seems to give no play. No sure how I'd check the linkage, tried poking it from the bottom where all the scottoil/road crud collect and that seemed ok as far as I could tell. Again I'm not a mechanic so not 100% if I'm checking these correctly as its still all new to me.

Chain is 800 miles old, spockets were declared ok by ddealer at the same time (as per my own visual inspection).

Not sure where the engine bolts and nuts are...I'll try and look tomorrow when its daylight!

Thanks for for suggestions so far though!