If you are seeking to replace the motor on your Dyson DC01, be aware there are two types. One is called a “YDK” motor and will have the code “YV940” on the side. The alternative is slightly larger, and is made by an Italian company called Ametek. Predictably, this has “Ametek” on the side of it.
The DC01 motors are quite sturdy units. They were used in the Dyson DC01’s back when Dysons were still made in England in the late 1990’s. However, fifteen years or so later, the odd one is starting to fail now.
They are still available new, but are quite expensive compared to the value of your Dyson DC01 machine now. Many of the ones available are cheap Chinese knock-offs that will last nothing like the period of time your old one did.
As the originals were so well built, consider buying a quality used one. Not only is it green as you are recycling, but life expectancy should be just fine as long as the one you buy is properly tested and not sparking near the armature when in use.
The picture below shows you the two different types. Make sure you know which one your machine uses. The one on the left is a YDK YV-940, the one on the right is an Ametek.