Post mortem findings
I got the head off easily, which was a relief. The Max Jax is great for this using my home made engine lifter. Note to self; get a bit of 35mm solid round bar as the 31mm bar tilts a little too much.
Looking at the head it looked OK although you could see that the front three combustion chambers had a lot more soot in them than the back three. Presumably this is the result of poor tune on the Strombergs. Looking at the bores they are nice and smooth with no ridges, but certainly not a recent rebuild. The distant tinkling of cowboy spurs was evident; wrong head studs with stacks of washers to take up the slack, and the torque on the nuts was all over the place; some were barely finger tight and some were almost impossible to undo.
The next step was to get the sump off and pull the centre main to have a look at the condition of the bearings and crank. As soon as I go the sump off it was clear that cowboys had been here before too. No lock tabs on any of the main bolts. Centre main cap came off easily and revealed...tragedy. +10 bearing shells and a pretty badly scored crank.
Any fantasies I had about poping in a set of rings and bearings and driving off into the sunset have been shot to bits. It's time for a lovely new rebuilt engine! Good thing I've got a spare crank...