Originally Posted by RF Whatley
Originally Posted by Stuart Kirk
That's a good idea. ET rotors on BSA twins are secured that way.
Sorry, sir. It's a VERY bad idea.

Also, ET rotors are TIMED using a single pin into the engine sprocket. That pin does nothing to keep the ET rotor from exploding.
Hi RF. I guess I didn't expect this to be such a contentious subject. I didn't mean it to be and I apologize. I do have additional comments.

Thank you for pointing out the pin's timing function but we must recognize that it also moves the drive input from the hexagonal core to to the aluminium body of the rotor. This actually eliminates the cam lobe effects of that 6 sided core that tries to push the magnets outward and possibly "explode" the rotor..

The spring washer strategy accomplishes exactly the same thing by by gripping the aluminum, not the core. NickL makes the same point and I agree with his thinking.
Originally Posted by NickL
The hex in the centre pushes the magnets out as the loose outer rotates on the hex,
they have nowhere else to go.........
If you stop the outer rotating on the hex they stay in place as designed. This
is done by locking the two parts together.

It seems that the overriding issue is to not let a rotor problem go too long. If you hear a worrisome noise from the lower end, take the time to find out what it is. The ones I have repaired have been loose enough to be audible and sounding like a rod or main bearing noise at idle or just above.