Hi Mark and Mike, thanks for your interest.
I know a bit about the Lister FR series and I was able to get this up and running in a couple of days. I needed to replace a broken piston, worn out rocker and the compression change over valve and combustion chamber plug. I made a de-compression lever, serviced the injector and fuel pump, a bit of fettling here and there and it starts first swing every time.
BUT I know NOTHING about generators.
This is a steep learning curve. I thought the capacitors stored residual voltage to energise the fields but it now seems very likely they are for suppression of interference. There were six capacitors, two in the shunt, two in the AC alternator and two in the DC dynamo. I removed them and still produce the same low voltage.
I have checked all circuits for earth faults and continuity. The field resistances seem to show there is no damage in the coils. I think I am missing something obvious and will keep investigating the problem.
I'll let you know how I get on, Reg