Wiring Diagram or Knowledge on speed control of Lister Generator diesel engine 7.5HP.

Have recently purchased 7.5HP twin cylinder diesel Lister that use to have 240 volt gen set bolted to the back.
On the engine there are two looks like solenoids that control the governor of the engine.
Set up looks complete but not sure on how the system works or wiring connections.

Wondering if anyone can help as reusing setup to run gen set.

Thanks Dutchy