Air release valve

[John Simpfendorfer]

Hi to all you knowlegable Forum readers.
Can some one tell me what the function is of the small steel ball and spring that fits the back of the flat screw which holds the timing gear on to the crank shaft.I have three motors and none of them have the spring/ball in them.
Will the motor function without them ?In the spare parts booklet it is listed as part no 505.
Are these parts available from the LDMCC.?

Also I have the remains of two Douglas carburretors nos.1879 and 2954.One with an updraught manifold.
Are there any drawings or details around of these carburretors?
Would be willing to swap these for a side draught carburretor and manifold.

Happy New Year to all forum readers.
John Simpfendorfer.

[eddie]

John,
        The ball and spring acts as a breather non return valve that creates a partial vacuum in the crankcase. This assists in drawing oil down from the drip feed sight glass. The valve vents the crankcase pressure (when the pistons near the bottom of the stroke) into the timing chest. This gas contains oil mist that keeps the valve gear lubricated. In the bottom of the timing chest there should be a short standpipe to control the oil level. There should be another pipe on the outside of the timing chest that routes any discharge so that it falls on the road clear of the back tyre!
  The ball and spring used to be a stock item in LDMCC spares.

  Regards,
              Eddie.

[John Simpfendorfer]

Hi Eddie,

 Thank you for your detailed info.on the "Air release valve".
Is it right to assume that the short fitting in the timing gear area would be approx.3/8" long so as to form an oil well that deep for the gears.

Cheers  John.

[Doug]

John,



Length also shown in this post:
https://www.douglasmotorcycles.net/index.php?topic=2811.msg10555#msg10555

-Doug


[update https link. 22Apr20 Doug]