I had an extra clutch side cover laying around, and i have read that some people wasn't sure how they blocked off the opening. So i decided to find out, and it was very ingenious as to what they did and i do have a pic to share just needs resizing.
When you look at the inside of the cover there appears to be either unfinished machining or a plug, and yes it is a plug. The only unfinished machining is the spot for the decompression setup they used on the kicker. On the outer side the plug is covered with a make-shift seal... either incase the plug comes loose or from keeping anyone from tampering by misleading them to think that it's not machined out.
So with careful use of a drill bit, i removed the make-shift seal and it took absolutely no effort to do. Once the bit catches it spins loose and can be removed with ease, then you'll find an aluminum plug that's stuffed in there. Turned the case over a few times to be sure which way it gets knocked out of the whole and it's ment to be pushed out from the inner side, hence that tapered look.
With a short 3/8 drive extension and light tapping the plug comes out and you now have the opening in the casing for your kickshaft and the oil seal.