B31 Dies and won't start - any ideas please?

[KernowPete]

s/a = swinging arm. Different (better) gearbox from the plunger and rigid models.

Thanks for that - mine is a plunger 

[V500]

s/a = swinging arm. Different (better) gearbox from the plunger and rigid models.

In what way better?

[scifi]

On the difficulty to start when hot.  Have you checked that the points gap is still there.  Also do you still have any tappet clearance..?
Both of these could reduce to less than zero, when the engine becomes hot.
Best of luck..

[Derek996]

s/a = swinging arm. Different (better) gearbox from the plunger and rigid models.

In what way better?

Better faster and more positive gear changes. Also more robust and reliable.

[V500]

I've ridden both and still have two plunger gearboxes, one on the Star Twin and the other on a Goldie, and I can't say there's any noticeable difference. The one on the ST is particularly sweet-changing.
Both have lasted for 73 years and counting, so maybe reliability isn't so much of an issue either..

[Derek996]

The Star Twin gearbox bolts onto the back of the crankcase and is basically the same as the swinging arm gearbox but in a different housing.