So it is chassis rather than engine knocking ?

I'm no mechanic either but..........

I'd be checking for play in the suspension linkage, give the shock,swingarm and linkage a good wiggle.Check engine mount bolts/nuts are present and tight, ditto the fork yoke bolts.

I'd also look at the sprockets and every link of the chain just to be sure.Check for play in the front wheel bearing too.