I've only ever seen them on early Nortons:


Bikes that were used in North Africa / Middle East had all sorts of contraptions...

email (option): wd.register@gmail.com

That's the one...I'd happily consider fitment of one to my M20 under the heading of 'artistic licence'...It probably happened anyway...By the look of some of the pictures I've seen I think filters were sourced from 4 wheeled vehicles in an act of desperation by REME ...I bought my M20 from an ex North Africa dispatch rider and he said engines only lasted a few weeks maximum without filtration...Ian

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

It seems they were only used on the 1936/37 manufactured WD16H machines.
1936 for the British Army and 1937 for the India Office as far as I can see.

Very nice Norton picture by the way!

There is a picture of a BSA prototype of 1937!

Cheers,

Rob

email (option): wd16h@telfort.nl

The discontinuation of air filter fitment is a puzzle to me. My understanding of all the MEE tests that I've seen suggests no loss of performance or increase in fuel consumption. They were fitted to several small contracts, saw a certain amount of Home Service and then suddenly on the MoS listings for C9681 in early 1937..."Air Cleaners are not now required on the machines". No indication of who decided this, and why. There was obviously an extra cost. Perhaps they decided that it was no longer necessary for Home-based machines.

Ian, sent you an email…

Thanks Scott...most helpful....Ian:relaxed:

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