Oil capacity issue in KZ650 1977

In order to drain all the oil, you most remove the drain plug ( number 22 in the diagram) and numbers 30 and 31, which will allow the removal of the oil filter and its parts.

www.kawasaki.com/Parts/PartsDiagram/144001/1977/KZ650-B1

baldy110 wrote: It's NOT going to be sludge buildup. Don't go there, whomever told you this knows nothing of these engines. I'm going to say it's probably something your doing.

+1
If there was more than 1.8l of sludge in the engine, the oil pump would be clogged and nothing would drain from the drain plug.