Hi all.

Got a question for the knowledgable people.

Currently my M20 is fitted with a 17 tooth engine sprocket and a 17 tooth gearbox sprocket. This is what it came to me with.

What should be fitted for a road going bike? I’ve read up in here which suggests these are wrong? but it’s not clear what combo l should use or have.

It’s also fitted with the later B/M gearbox if that makes any differance with gearing?

Thanks in advance

email (option): Mdmax72@icloud.com

A 17T engine sprocket is listed for low gear sidecar work. A solo WD M20 had an 18T engine sprocket for military use but a 19T would be more appropriate today. The gearbox sprocket was always 18T. I don't think the post war M series box is any different gearing wise. Ron

email (option): ronpier@talk21.com

The post war gearbox had the same internal ratios..Postwar a 19T gearbox sprocket was the standard fitment...18T for a wartime military machine....Note, however, that the post war gearbox was fitted with an oil seal whereas the WD box was not...So, for a postwar box a sprocket with a plain 'inner shoulder' is needed for the seal to run on whilst the WD box, which doen't have a seal, has a scroll machined onto the inner shoulder of the sprocket...Ian

Wartime contracts fitted with chairs had following spec
Engine sprocket 16T
Gearbox sprocket 18T
Wheels WM3 x 18

Br
Job

email (option): Jonnyob1atgooglemail.com

That's interesting John. My list for the RAF outfits with 18" wheels quotes a 17T engine sprocket? Ron

email (option): ronpier@talk21.com

Thanks for your time and knowledge gents.

So ideally l should be looking for a 19 tooth gear for the engine and a 18 tooth for the gearbox.

email (option): Mdmax72@icloud.com

Sorry Ron
A 17T is correct
My eyes 👀 again

Job

email (option): Jonnyob1atgooglemail.com

email (option): ronpier@talk21.com