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Reference => Douglas Motorcycle Technical Articles => Topic started by: Doug on 10 Jun 2007 at 03:08

Title: Drawings for non-return oil valve, Models CO, 600EW, F28, 350EW
Post by: Doug on 10 Jun 2007 at 03:08

Here are the drawings for the non-return oil valve as screwed into the front cylinder on certain models. Two versions are shown, which except for the lower housing, share identical parts. One uses a 7/16-20 thread, and is as used on the OC, 600EW, F28, and probably other Douglas big twins of the era. The 350 EW needed a special lower housing to clear the adjacent cylinder hold down nut, and smaller, shorter thread to cope with the thinner cylinder wall found on the 350cc barrels. Apparently this is the same as used on the 2-3/4hp models.

Below each is a link to a PDF version (Requires Adobe Acrobat) that you may find easier to print.

(https://www.douglasmotorcycles.net/aa-files/images/doug/2007/non-return-valve/check_valve-01.jpg)
Downloadable PDF file (https://www.douglasmotorcycles.net/aa-files/images/doug/2007/non-return-valve/check_valve-01.pdf)

(https://www.douglasmotorcycles.net/aa-files/images/doug/2007/non-return-valve/check_valve-02.jpg)
Downloadable PDF file (https://www.douglasmotorcycles.net/aa-files/images/doug/2007/non-return-valve/check_valve-02.pdf)

-Doug

02Jul10  Fix typo, add reference to 2-3/4hp models. -Doug

Title: Re: Drawings for non-return oil valve, Models CO, 600EW, F28, 350EW
Post by: Petethesign on 31 Dec 2014 at 07:45

Thanks Doug
Exactly what I needed.

Title: Re: Drawings for non-return oil valve, Models CO, 600EW, F28, 350EW
Post by: Neilj on 24 Oct 2021 at 07:47

Thanks looks complicated going to have to find a good machine shop