I just started work on the 914 I purchased a few weeks ago. Just as I was diving headlong into re-installing the factory distributor to get it running, I realized that the timing hole plug is missing. I suspect that it has been missing for several years. A new one is on the way, but I'm concerned that there could be debris or other foreign subtances in there. Any suggestions before I re-install and attempt to fire it up?

You'll probably be fine for the time being, watch out for the engine running warm (but it shouldn't be much warmer at all). Anything that could drop in that hole could just as easily fall to the front of the fan and get in too.