Kz305, rocker arm shafts vibrating

Hey everyone, I picked up an 81 kz305 about a month that ago as my first bike and have been working on getting the thing in solid running condition. This forum has been amazing in this regard.

A few days ago I thought I had all my bigs squashed (timing, points, oil, carbs, electrical, valves, etc). Anyway, I took the bike out for about 5 minutes and noticed that there was a significant oil leak from under the points cover. I am guessing this is most likely the camshaft gasket, which I have on order. However, when I had the cover off and the bike running, I noticed that the inlet camshaft rocker arm bolt-end would rotate back and forth in time with the engine whereas the exhaust rocker arm bolt remains stationary.

The question I have is is it normal for the rocker arm shafts to rotate back and forth like this? How do I go about taking care of this? Is it possible that my oil leak was coming from the rocker arm seals and not the camshaft gasket? Is it possible to replace the rocker arm gaskets without pulling the head?

Any insight you can provide would be awesome.

-zac