Author Topic: 1920 2 oil valve disc modification  (Read 268 times)

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Offline Peter G

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1920 2 oil valve disc modification
« on: 13 Oct 2022 at 01:59 »
Hi All
Ive recently purchased a 1920 2 and am working my way through familiarising myself with the machine. The oil non-return valve was not functioning correctly so I pulled it apart and discovered the disc had been modified with a series of notches (see image). Has anyone seen something like this before and would anyone know why this might have been done?
Thanks in advance


Image converted to linked file. Please see Taking photos with mobile/cell phone - Dave, 13Oct2022
« Last Edit: 13 Oct 2022 at 08:12 by Dave »

Offline Hutch

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Re: 1920 2 oil valve disc modification
« Reply #1 on: 13 Oct 2022 at 04:52 »
Hi Peter and welcome to the forum and an interesting question!

I have not seen valve discs modified like this before and can only guess at the possible reasoning of the person who modified it. Quite often these discs are missing and I have only come across one that has been modified and that was in the valve at the bottom of the hand oil pump in the tank. This has had a small hole punched in it (see picture) I have no idea why this was done and would most likely cause some oil to be draw back into the pump from the oil sight when the pump is lifted to refill from the oil tank, rather than heading on a one way trip to the engine as it should - but there may be a perfectly logical reason for it?

One thing did come to mind when I dug the bits out for the picture, is that the discs in the non-return valve are smaller diameter that the ones in the oil pump. I don't know the diameter of your disc, but if it was a spare one out of an oil pump, maybe it was modified to suit the one way valve? A simple measurement could give a clue or blow my theory out of the water! :-).

There is a screw-in brass disc seat in the female threaded half of the one way valve (didn't come out well in my picture and it wouldn't unscrew easily - a common problem with 100 year old brass parts). If that is missing and the bigger disc from an oil pump is used, then that might explain things, as the little "V's" in your disc, would help let the oil get past when the disc is off its seat (on the male threaded part). This job is normally performed by two slots in the screw in brass seat insert and the bigger disc would not fit in the recess.

As long as the little "V's" don't encroach on the hole through the male threaded part then it may actually seal ok???

If the disc is 3/8" diameter then my only other guess on the purpose of the little "V's" is to allow for extra oil flow through the valve when trying to refill the sump after it has been drained with the obligatory 3 full pumps of the oil pump and the ambient temperature is low. As mentioned above if the "V's" are not deep enough to allow oil through to the hole in the male threaded part of the valve when it should be sealing, it may well work ok (??....and maybe not!)

I would be interested to see what others think (...and happy for my theories to be debunked! :-) ).

Edit:- I just had a closer look at your drawing and possible the spring is not on the correct side of the disc?? Cross section of valve here;

https://www.douglasmotorcycles.net/index.php?topic=2140.msg7758#msg7758

What Doug refers to as the "cage" is the screw in brass seat I referred to above.

cheers

Hutch
« Last Edit: 13 Oct 2022 at 23:37 by Hutch »

Offline eddie

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Re: 1920 2 oil valve disc modification
« Reply #2 on: 13 Oct 2022 at 08:48 »
I have seen discs with 4 flats to allow the oil to pass when the disc is a neat fit in the cage. One other thing I did notice is that Peter's valve assembly has a rather strong spring - maybe, too strong for the pressure from the oil pump to overcome it. Also, attention to the non-return valve in the timing end of the crankshaft can improve the crankcase breathing, thus assisting with drawing oil down from the tank.
       Hope some of this helps,
                                           Regards,
                                                        Eddie.

Offline Doug

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Re: 1920 2 oil valve disc modification
« Reply #3 on: 13 Oct 2022 at 13:31 »
Might want to review this post:

https://www.douglasmotorcycles.net/index.php?topic=2140.msg7758#msg7758

The disk does not need notches as the oil bypasses via the slots in the cage. Unless someone has replaced the cage with one lacing slots.

Though for the 350 & 600 EW, the 350 EW non-return valve probably carried over from the 2-3/4hp models.

-Doug

 

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