Hi David

Steve.S has provided the correct ebay UK ref. no. Try the full link below:

Vintage BSA M20 oil tank with cap . Note likely model fitment differences

email (option): steve@bsa-inc.com

And this guy in Greece is selling what he calls a KM20/WM20 oil cap??? This looks like one of the Westwood caps as fitted during post war REME rebuilds.

The KM20 oil and Petrol caps have a bigger pyramid piece under the "T" handle than a WM20. Ron

https://www.ebay.co.uk/itm/166512794119?hash=item26c4ef9a07:g:dkkAAOSwkIBlWjBW&amdata=enc%3AAQAIAAAA4J%2BMpnBRTJpM2qtFig6CGN%2BhVXzN%2F5cUmKFX%2Bi1aLlUAUrRWWiTDCRhTax1aEHpi8mxe6CplCfzpklNocqAEryOZJG5KY35QfmxFTk2WycWebQyWEXGikQatTV6glQAWuizcYM0yExhHRRCw9d7XYHUNUC8kZ%2FrYbxKjHheqrSuLTn5oIRaYyXKHNJ0ZxnXkm37gp0ZwM1Fzqwj3bIgEqm8if%2B%2FOawVIl%2B1T3znrU2T6amqlDGkoXhj8OCRzX0nVDgKuU1CjH52r7lpjK9jj2Dsr1IzbrSKrgD88Vwk0WlZc%7Ctkp%3ABk9SR_7tl9CUYw

email (option): ronpier@talk21.com

Hi Mike, I don't think that the actual oil tank is different, but with that type of drain plug and the green paint it most probably was fitted to a KM20, I've never seen that type of drain plug before I saw the KM20 poster /chart.