Some explanations needed here.
Firstly, the cooling system.
As mentioned i my previous post, the best way (IMO) to cool this engine is using the thermosyphon method. The thermosyphon effect is self-regulating; ie. the hotter the engine gets the higher the coolant water flow rate goes (up to a limit defined by the width of the pipes and channels through the cylinder head and radiator). The thermosyphon effect even negates the need for the thermostat. When the engine is cold (which is when the thermostat does its job and stops the flow), there is no thermosypon flow.
A little more info about the machine before describing the pump pulley system.
These generators are multi-speed machines. When I say this, I do not mean that the running speed varies. I mean it can be set at different speeds. The speed settings are 1000, 850, 650, and 400rpm, and the generator comes with a set of pulleys to allow the alternator speed to be 1500rpm whilst running at any of the above engine speeds. The idea here is that you can setup our generator to meet your needs, which will vary over the seasons. In summer you may only need 1kW from your genset, but you have the ability to get much more from it when you need it - in winter.
There are several advantages of running your engine slow when you need less power:-
1) The wear on the engine is reduced and your service interval increases.
2) It produces less noise.
3) The pumped cooling system works appropriately for the engine speed - you won't over cool your system.
If you live in a cool climate (e.g. the UK) and you don't usually run it above 850rpm, then it is recommended that you do not use the coolant pump - just rely on the thermosyphon. However, if you live in hotter climates and want to run the genset at full-power, then you should use the pump, and you have a selection of pulleys to get the engne temperature exact - but the choice is yours. If you don't use the pump, then you don't need a thermostat. Also, these engines are not started and stopped as frequently as automobiles, so we thought a thermostat would not add much value.
The starting and stopping.
Both stopping and starting is done by the control panel. Stopping is achieved by the use of a solenoid that closes the rack. This allows the control panel to monitor coolant temperature and lubrication oil level. It also means the genset can be started and stopped by a timer or an inverter.
Mark