The manual for this bit of kit is Book 495/964, and covers single-cylinder 1-3/3kW and twin-cylinder 4-1/2kW sets.
The operation is almost identical to the standard Start-O-Matic sets with one big difference.
The alternator is a unit power factor type, that is: it is intended for use on mainly resistive loads such as lights and heaters, use on inductive or low power factor loads will result in poor voltage regulation unless power factor correction capacitors are used. This istated in the book.
They were available with 110V or 240V output.
If you are having problems with just lighting (bulbs, not flourescents) loads then it may need looking at, but if you are putting inductive loads such as motors of flourescent lamps on, then that may be your problem.
I'll check and see if the schematic in the book is the same as the one on the website.
I asked about your location in case it made a difference, but it doesn't.
Peter