I've just had a look in the tappet covers of my rebuilt C15 after running it for five minutes or so, and it looks pretty dry in there. I was expecting/ hoping to see everything covered in a film of oil.
Before first start up I put perhaps half a pint or so of oil in through the tappet covers to drain down into the sump and submerge the pump. An hour or so later I walked the bike about in second gear with the plug out for a couple of minutes to fill the sludge trap etc. On start up oil flowed immediately out of the return pipe, which I blocked with my finger for thirty seconds or so to force oil up into the rockers. But I have no evidence that this has actually worked.
I know that I can slacken off the banjo nuts to confirm oils is reaching that point - and I will do that at the next opportunity. But is there any way of confirming the rocker oil is lubricating the tappets / valve heads etc? If I ran the bike with the tappet covers off should I be able to see a spray of oil?
I don't think you'll see a spray , rather a general moistness up there.
Once you've slackened off the banjo nuts and oil is dribbling there you can't do much more.
A longer run should get more up there
Just to close this thread off. I completely dried off the valve collars, inlet and outlet, and refitted the caps. I also loosened the banjos. On start up the banjos instantly weeped oil, so I shut down and retightened them. I then ran the bike again for a minute or so. On removing the tappet covers the valve collars were moist/wet with oil. So I am now totally happy that all is as it should be.