Re: Excuse my stupidity, but what's a Clutch?
In short, a clutch is a device that helps to engage/disengage a source of power and connecting it to a source of movement/expidenture of work. In these motors a centrifugal clutch is used, the transfer of power is made by having a few pads that are connected together on the driveshaft by few tough springs that expand as the speed of the driveshaft increases. As the speed increases the springs are no longer strong enough to hold the pads together and they start to spread apart and eventually come into contact with the inside wall of what is essentially a tube. When that happens the "tube" starts to spin and you have movement of your chain/belt/mower blades/string trimming wire or a thousand other applications. A google search can fill in details but the above should work as a basic level of understanding. = ) Hope I helped!