Main bearing circlip
 
The original circlip (65-2240) that holds the outer left hand main bearing in place is about impossible to refit without putting aluminum shavings into the bearing. Go to your local bearing supplier with the crankcase and the old circlip and ask for a modern circlip of the same size (the type with an eyelet in each end) and buy a decent set of circlip pliers to suit. You might need to linish the outer edge of the circlip slightly to fit in the existing narrow slot, but it can then be fitted & removed with no further problems.

Use a 54mm diameter external circlip. (i.e. to fit a 54mm bore). It is actually around 57 mm external diameter as bought, to allow it to be compressed & subsequently sprung into place in the machined groove in the crankcase.  These are 2mm wide. (About 0.080 inch).  They can be purchased at any bearing supply specialist for a very modest price.

The original BSA circlip is 1/16 inch wide. i.e.  0.0625 thou or around 1.5mm; so the new item will need to be reduced in thickness to match the original. This is easily done on a linishing (or sanding) belt in about 5 minutes.

Using a suitable pair of circlip pliers, it is very easy to fit/remove the new circlip without contaminating the open side of the new bearing with aluminium slivers or debris, which certainly is not the case with the original BSA item.

 
 
 
BSA WDM20 Reference Material
 
G’day folks:- My name is Mike Jeremy; I live in Cairns, Australia. I’ve run a 1953 M20 for 20 + years & am slowly restoring a totally worn-out 1941/42 WM20. Henk’s web-site has been a great help with the latter. I am secretary of the local motorcycle restorers club & part of that task is to be custodian of a well – indexed library of several  hundred U.K. ‘Classic Bike’ & ‘Classic Motorcycle’  magazines, that is essentially complete from the present time back to around 1981. (Plus a few other titles as shown). During the rebuild of my WM20 I have checked through these magazines & as a result, listed below are articles that relate directly or generally to the WM20/M20 range & could be useful to other owners. There may well be errors & omissions.


As copies of these old magazines are often available at swaps or autojumbles, they may provide some reference material for rebuilds, colour schemes, or general background information on our favorite bikes.

CLASSIC BIKE:-Feb/March 1981. General girder-fork renovation article. April 1984. 3 page road test. B & W photos.
Nov. 1984. 3 pages. Owners tips. B & W photos.
June 1994. Road tests of 6 WW2 military m/c’s. Not WM20. Colour pics. July 2001. 1 page on ’44 WM20. Colour photos. June 2003. 5 page buyers guide M20/21/WM20. Colour.
June 2004. 8 pages. ‘Return to Normandy’ article, & several WW2 military bike comparison, incl. WM20. Colour.

THE CLASSIC MOTORCYCLE. Sept. 1986. 6 page article on WM20. B & W + colour.
Jan. 1987. RAF WM20 & Indian. B & W + colour.
Dec. 1989. 4 page road test of restored civilian 1946 WM21. Colour.
Feb. 1993. 3 pages. Road test of ‘Radco’s’ bike. B & W + Colour. Aug. 1999. 5 pages. Various military m/c’s at war incl. WM20.
April 2003. 6 page road test of restored civilian 1946 WM20. Colour. 

CLASSIC MECHANICS. April/May 1987. Excellent 5 page WM20 restorers notebook/tips by ‘Radco’, including detail on girder fork restoration. . B & W photos. 
CLASSIC BIKE GUIDE. June 2004. 2 excellent articles on WM20’s & other WW2 military m/c’s. Colour.
 
Also in ‘The Classic Motorcycle’ of Dec. 2004 is an article on the Ariel W/NG model, & in Sept. 2005, the Royal Enfield WD/CO is featured. 
 
I trust that the above information is useful.