Hi all I have been trying to source some photos of a 1938 m20 for restoration purposes.I have seen a few bikes claiming to be 1937 but they look like WM20's and appear to have the wrong head, barrels, timeing gear cover and oil tank/frame as i believe they differ from the WM20 and the parts I have are definetly different in apperance. But in saying that I'm no expert, so would be greatful for any assistance. Thanks Graeme

email (option): smith.g.m@bigpond.com

Hi Graeme,

The 1937 and 1938 M20's are quite different from the later type. The engine has the 8 bolt head and the tappet case is one with the cylinder. In the later types there is an air gap between the cylinder and the tappet case. The engine has a different entirely flat timing case which also has a slightly different shape. The timing cover is not interchangeable with the later type. The cams have spindles attached and run in the timing cover. There is no support plate like on the later types. It is a pain taking the timing cover off and have you cams drop out every time if you are not careful enough. The spindle type cams come in quite a few guises so you have to take care to find the right types. The profiles are all different. I have a box full of that type but there is a difference between the B and M group cams to start with and even the M group cams come in 3 types.

Another very noticeable difference is the oiltank which is attached to flat strip like lugs attached to the main frame triangle. It is of a smaller capacity than the later type. The oil lines should be the all hose type and not the later copper pipe with rubber sleeve type. Should I continue? All in all a different bike and much rarer than the WD M20.

Regards,
Leon

email (option): leonhop3@planet.nl

Graeme, I have sent you a couple of shots of a friends 1937 plus one from 'somewhere on the internet'.

email (option): rays54@hotmail.com

Leon, please continue....

email (option): unpob@yahoo.com

Nice pics of '38 M20

http://de.wikipedia.org/wiki/Birmingham_Small_Arms_Company

Henri,

No problem. The bottom of the front down tube is a plug with the lug for the engine plates instead of a ring like on the WD M20. The rear frame section has a lug on the other side of the part that goes around the oil pump instead of a pressed tube. The rear frame also has a sidecar attachment hole at the back on the left hand side. The magneto is the early MO1 type which has a different base and also a different cover. The rear hub to brake drum bolts are the early flat type which have a 3 layer thackeray washer underneath. The crankcases have a banjo fitting at the oil pump housing for the take off for the oil pressure indicator in the instrument panel. The toolboxes are of the triangular type and fitted on either side near the top of the rear mudguard. The silencer is of the fishtail type. And so on and so on...

Regards,
Leon

email (option): leonhop3@planet.nl

To cover this subject thoroughly would require a write up of the full spec. of both types....virtually nothing remained unaltered when Val Page and Herbert Perkins got hold of the early M20 and re engineered it into the more familiar type....Ian

email (option): julie@wright52.plus,com

Thanks Leon, will copy and scrutinized in the morning.

email (option): unpob@yahoo.com

where else can you get such accurate information and all at no cost

thank you Leon, most interesting that

JO'B

email (option): jonnyob1@googlemail.com