I have now seen two WM20 frames with an irregular hole in the upper rear frame lug (the casting where the top and gearbox down tube meet). Both these were on the top above the down tube, are these meant to be there or are they just broken?
Cheers Pat

The holes are meant to be there..I think they were predominantly on the earlier frames...Ian

email (option): ian@wright52.plus.com

Yes, I think all WM frames without sidecar lugs have that hole.

Another interesting difference in both frames is the thickness of the tubing. In the plainframe the top-tube has a thickness of approx. 1.6 mm whether the sidecarframe has a tubethickness of around 2.6 mm.



Also note the presence of a the brass "cap" at the end of the tubes in the headstock, that probably saves pumping the tubes full when greasing the headstockbearings.

Cheers, Michiel /NL

Hi Pat
i can help you about the front frame -
if u interested i can send some photo to u
cheers . Hussein

email (option): sl_hussein@yahoo.com

Now found out that the great difference in the tubing gauge (see picture above) between the sidecar frontframe and plain frontframe only goes for the early WM frames as the later plainframes has the thicker tubing. This can be easily checked by looking into the hole below the saddle.

Also there is a difference in the tubing gauge between the early and later rearframes.

I will weight and compare them both when I have to opportunity, but the small weight of the early WM20 frontframe is allready striking when you have them in hand.

So it looks to me that BSA did use the light weight M24 goldstar frame 1:1 into the early WM20's, thereby giving up all the sidecarlugs, the pillion footrests and the small-propstand lug below the brakepedalpivot.

Maybe to meet up with weight demands from the War-Office?? Any thougths ??