When I fitted my new totally rebuilt engine, with a Weber head, I had problems getting the gearbox to mate up properly with the engine, but eventually it all went together.
Then, when I tried to set the static ignition timing, I found the flywheel had been fitted 1 bolt out of position, (60') so the timing marks seen through the gearbox hole didn't line up at TDC.
I tried timing the engine, but despite starting easily, it just would not rev, and spitted flames out of the DCOEs.
No other remedy than to take the gearbox off and move the flywheel round 1 bolt hole to the correct position. The gearbox came out in about 90 minutes, the clutch was taken off and then I noticed the spigot bearing was horrible.
Instead of an O shaped bronze bush, it looked more like a snails shell. A phone call to Richard to order a new one, and he explained that the gearbox 1st motion shaft slops around and sort of reams out the spigot bearing. He sells roller bearings instead of bronze bushes. These need the flywheel machining, so off to the machine shop soon to get the centre hole enlarged, and the new roller bearing fitted.