Auto Advance Unit

Yes, replace the springs if you don't know the history on them. They do weaken over time and as far as I know there's no test for them, at least I haven't heard of a test. And do make sure that advance cam is not loose on the shaft. Believe me, a dwell meter will tell all, even a strobe will tell. You'll get wandering timing. I gave up on them and got a Pazon. Couldn't be happier.

With all due respect to those who happily and successfully run points and an AAU,
save yourself a lot of time and aggravation and install an electronic ignition.......
or spend the time to become an expert on points and AAU, which does work quite
well, and you might save $100.

Thanks for the link to the AAU. A new AAU costs 99.80 £ and a new Pazon Sure-Fire costs 104.50 £. Unless I'm missing something, it looks like for an additional 4.70 £ I can upgrade from the points /AAU system to electronic ignition.

And the Wassel Vape electronic ignition is even cheaper. I replaced my 40 year old RITA ignition with the Vape one and it seems very good.

Ian