Phew! .... it's just a hole in the engine.

Yesterday was the first opportunity to fire up the bike and check that everything was ok. For the first time ever it wasn't so keen on starting, and it sounded just plain wrong. It wasn't running on all 4 cylinders so a fresh set of plugs and try again. Same thing, we tried quite a few things but couldn't suss it out and eventually after checking ignition and cam timing and finding nothing wrong, i gave up deciding I'd had enough.
After all the hours spent being meticulous and checking everything goes back together properly, its a bitter disappointment when it doesn't even run properly. And as a wind up when i got home my tickets for Shakespeare county raceway had arrived. I thought at that point i wasn't going!

This evening was time for some more investigation. There was compression on each cylinder but i noticed yesterday when i ran the bike out of fuel before putting it away that one carb still had a lot of fuel in the floatbowl. Lectron carbs don't really suffer from blocked jets (they don't have any) so i knew it wasn't the carb. So i checked to see if there was a good vacuum on that cylinder whilst turning the engine over. The result was nothing! Immediately i suspected a valve not closing , perhaps bent even so the head was removed.
And the culprit revealed itself! A piece of epoxy on the outside of number 3 intake was missing and a decent size hole was left in its place, letting air straight through into the intake.
I cleaned it up and re-epoxied it, and tomorrow i'll refit the head once again. It might be ready after all!