i have rebuilt my engine had some knocing noise replace balace chain as it was toching casing put back togeta still knocking so stripped engine big end bearings going so replaced big end barings main bearing rebuilt head put all back togetha new cam chain timed it all up turned it over by hand and as i turn it over i get slack at the bottem about half a link and as i go around it goes slack between cams spoke to a mate he said its ok needs oil pressure so put it all back to getha all ok no knocks until u lift the revs knocks abit any indears been told it could be the crank or the cain help plz