Late 1960s and 1970s singers

Someone gave me a Singer 9000 a few weeks ago and it gave me the idea of showing you how to replace the broken plastic gears.

In the example, a 9000, none of them were broken but one was seriously discoloured, which always meant it was very brittle. So I decided to replace just that gear.

Here it was beforehand.

and afterwards 

Now getting from the first to the second requires that you either follow the service manual exactly or you know how both feed and hook timing work.

Tricky things are whether the securing screws are facing up or down and the present position of all shafts when the old one is removed. You need to remove both shafts to allow the release of the brown gear. I marked them by scribing but still mucked it up and had to correct.

In short, you need to release the back shaft mountings, both of the bobbin drive gears and the gear on the right with the belt. Marking them will make the work much easier but remember that the needle tip and feed dog sink beneath the needle plate at the same time ;-)