So.... Got it all back together over the weekend (thanks Val!). I used silicone grease on the gaskets and and the cone rubber on the bolts (which i've done before). She started up first time, sounds really sweet and was left ticking over until three bars came on the temp gauge - no leaks, so happy days.
Went for a short (15 mile) ride to my old man's house - there was a very thin film of fresh-looking oil under the LH cylinder on the edge of the fins. Hmmmm. Wiped it clean but couldn't see an obvious source, and there was some obvious silicone grease still in the area which had obviously worked it's way out under heat. Anyway, got home, checked it and found another thin film with no obvious source again. Grrrr. Had a brew then decided to whip up to Haworth for an excuse to head out again. 25 miles there....checked it....thinnest film yet with a tell-tale tiny dribble coming from the lower front bolt on the LH rocker cover...the one I snapped and replaced. I (sensibly) this time didn't consider any road-side tweeking, but gave it a good wipe down and rode the 25 miles back home.
Nothing. Not a drop when I got back.....
I'm hoping that the rubber on the bolt Val sent me was just bedding into the rocker cover, and that as the bolt got hot it caused some of the grease to work it's way out along the shaft of the bolt, dragging a bit of the oil with it by capillary action. As the last of the grease came out, i'm assuming the rubber finally bedded against the cover and sealed it tightly.
I haven't tried tightening it at all, and haven't ridden the bike since I got back. It'd also be safe to assume that I was extra-cautious when I nipped this particular bolt up, so it may actually be not quite up to torque, but i'm going to keep an eye on it and see if the issue returns.
That said, i'm pretty chuffed right now. The bike ran as sweet as a nut, and it's once again got me thinking whether I actually need to keep the Blackbird or not.....
