Someone told me that the fiber gear is installed by Lucas because of isolating issues.
But why is there a clutch installed? What can damage the dynamo?
It is a simple design mounted between 2 bearings.
So where’s the weak link?

The clutch is there in case the dynamo seizes up or if there's a sudden heavy load on it.

Hi Keith.
What do you mean by "dynamo seized up"?
And what sudden heavy load do you mean? These engines are slow and steady.
Thanks for your time.

I think if you put all your lights on and the dynamo is struggling to keep the battery charged up, there can be a severe electronic/magnetic load from the dynamo. Better that the clutch slips rather than the engine stops. Noam can explain it in more detail. Ron

email (option): ronpier@talk21.com

The clutch has to be there to isolate the drive from the dynamo in the event of a dynamo problem...

One problem a dynamo can have that will cause a 'siezure' is the breaking up of the commutator and that does happen occasionally...

There is also a very small clearance between the field coil shoe plate and the armature...A bearing failure can cause the two to contact also resulting a seizure or partial seizure...Ian

email (option): ian@wright52.plus.com