Well, it was time. I'm one of those insecure types that can't let a known problem fester, even if it is a rare occurrence. The NSU screws would have to be looked at. Just back from the Georgia BMW rally so an oil change was due anyway. Here's how it went:
First step is to buy one of these. Yeah, I know some people say the old one can be reused. I can assure you that is not always the case.
Next, drain the oil, remove the filter.
Then, remove the brake lever. I have Pro-Cycle's lowered footpegs so it can remain in place. With stock pegs you will need to remove the right one.
Now remove both oil fittings and the clutch lever. Detach the clutch cable at the handlebar end first.
Using an 8mm socket, remove all the case cover bolts. Important tip: there are FIVE different type bolts here! Keep them straight.
Next, use a plastic or wood hammer to GENTLY tap the case until it breaks loose. This thing is either aluminum or magnesium so don't hit, just tap.
Now look under the clutch. See that hole? Stuff a clean rag in it to keep junk out of your transmission. Then remove the four bolts holding the clutch plates on.
Different view of the clutch and rag. After removing the plates, bend the locking tab out and remove the center nut holding on the clutch basket. I used an impact wrench and either a 1" or 1 & 1/16" socket, I forget which. I just held the clutch hub with my fingers and a rag.
Next, using an impact driver, remove the oil deflector.
Prepare your M5 - 8 x 20mm bolts. I used stainless because I already had a couple in the garage, but anything will do. Not hardened though, because drilling the holes is tough enough in mild steel.
A little Locktite medium strength:
And a bit of clumsily-tied safety wire:
My project required a new gasket. Being a pessimist I had ordered a new one from Pro-Cycle a while back. Carefully clean up both surfaces using a gasket scraper and/or single edged razor blades. Other than that, reinstall parts in the reverse order and Bob's yer Uncle, it's done!
Oh, yeah. The original NSU screws? They were still snug at the current 1900 miles. Would they have worked loose? Beats me.