Advance/retard unit

Do you mean the shaft that has the cam that operates the points? If so the manual says to use an extractor bolt 06508. However, the shaft is a taper fit onto the end of the exhaust cam shaft and I found that by unscrewing the central bolt holding the points cam shaft a few threads and tapping it LIGHTLY with a hammer that it broke the taper by shock and it came out by hand. The actual advance and retard weights and springs are held on the rear of the plate that holds the points and comes out with the shaft once the plate retaining screws have been undone.

If that method does not work you may need to obtain an extractor bolt.

Dennis

A light tap as mentioned by Dennis has always worked for me. The Maintenance Manual says " Remove the central bolt securing the cam and automatic advance mechanism to the camshaft and obtain a piece of steel rod about 1/8" diameter and sufficiently long to stand into the internally threaded portion of the cam when pushed home in the hole from which the bolt has been removed. The outer part of this hole is threaded 5/16 in. by 26 threads. There are many bolts on the machine employing this thread,one of them should be removed and screwed into the centre of the contact breaker cam in order to extract it from the camshaft."

So you don't need to buy any very special tools for the job.