Morris Minor Owners Club

My rotor arm shows about 4mm burn/usage and the rest looks new. Is it too far advanced or retarded and how many clicks either forward or back on the micrometer should it go or is it ok where it is?

It is normal and not an indication of your timing being out. I rub the brass on the tyre tread to clean it. If too burnt, buy a new one.

Thanks beero, but what if the 4mm burn is on the right edge?

To adjust where the spark occurs relative to the rotor arm, you need to adjust the position of the baseplate in the dizzy, and then rotate the dizzy to compensate the timing back to where it should be...

Personally I've never worried about it.

If the timing is right where it is you may need to take the distributor out and move it one tooth where it engages with the camshaft.

not sure if the timing is spot on, but then, not sure where the burn on the rotor arm should be, and how wide it should be, should it be in the centre? can you "read" the rotor arm to tell if the timing is too retarded or too advanced?

When I was in the Scouts we were taught to find North with a watch or tell the time from the position of the sun. Never tried telling the time with a rotor arm.

Moving the dizzy round one gear tooth won't make the slightest difference! As Ray mentions earlier - you can slightly move the baseplate relative to the dizzy - by using the knurled adjuster. And then if need be - move the whole dizzy round slightly in the clamp to keep the timing spot-on. Have you checked if the vacuum advance is working as it should ? And is the mechanical advance working correctly - no springs missing or broken ???