The minor problem of the Layshaft support or countershaft.

Stripping my second motor showed  a problem with the layshaft or countershaft. The double gear column lacked the lower shim and there were clear wear grooves on the collar of the layshaft with some marks opposite, on the case. 

Layshaft suport (gears removed) there was no shim on this lower collar and wear grooves are evident on the collar upper surface.

Investigation showed the shaft itself, which is pressed into the rhs case, was not pressed in right up to the collar, although it was pressed in flush with the case on the other side. There was a clear gap between collar and case easily accepting a 0.7mm feeler gauge. 

Base of layshaft, clear gap between the collar and case beneath

Base of layshaft viewed from the other side- end of shaft is flush with case.

Test fitting the gear column showed that in fact it could not fit into the cases because when positioned on the countershaft; the gears kept the cases apart. This is probably why the lower shim had been omitted, but even so the gears were still too high for the available space in the case and dragged significantly on the cases when rotated thus accounting for the wear grooves on the collar. The height of the gears must have prevented close fitting of the cases and probably accounts for the signs of gasket leakage on this motor.  

I heated the cases to 100 deg in a water bath and then selected a deep socket to sleeve over the shaft and bear on the collar. 

Deep socket used as sleeve over the layshaft to bear on the collar itself before using the 10t bench press.

I used a large socket beneath so that the end of the shaft could project slightly below the metal of the case. The shaft pressed in to its lowered position with relatively little force in the press although I had failed to move it in the bench vise. 

Shaft pressed home, collar flush against case.

Base of layshaft support now protrudes slightly on magneto side of case. It's base is visible app. 9 O'clock. 

In this lowered position the cases could close over the gears which remained free to rotate. However, when I fitted new shims above and below the gear column (as the old ones were either very worn or missing) and compressed the cases together, the gears did lock up. This I found was alleviated when the gasket was included.  Overall I think its a toss up as to whether it's better to push the shaft down and fit the extra lower shim, or just run without shimming the bottom. I think its even possible that the shaft had been positioned to eliminate the requirement for the lower shim at the factory, although I can find no mention of that approach. In the end I chose to run with the shims and it's worked out fine.