Dominic, go to the "manuals & such" section & look at the Company Brochure. The pages that show the bump test (BTW, check out the spoke pattern on the front wheel on that test bike), and the page farther down that shows the "super delux" model. All 3 pictures have good images of the oil bath aircleaner.
These are early bikes in the brochure. You'll notice the aircleaner is above the rear upper frame bar. Later (probably your model K) they moved the aircleaner straight down & nestled it between the rear upper bar and the rear lower bar.
Mike Sal