Crankcase oil breather for 1926 OHV

looks the same as I remember on my father's 1949 International.  It has a spring loaded ball inside, and allows almost nothing to pass through it. That helps keep crank case pressure up, and promotes leaks all over the place. Especially noted on Inters!

Much better is a PCV valve like this one:

https://www.bskspeedworks.co.uk/pcv-valve.html

Paul Norman sells this. No spring involved.  https://racingnorton.co.uk/epages/4c675e64-813f-4c0a-8926-87a680c962a0.mobile/en_GB/?ObjectPath=/Shops/4c675e64-813f-4c0a-8926-87a680c962a0/Products/%220248+A2/707%22&Locale=en_GB

Hopefully someone will confirm. My Inter has a very early engine and this breather is horizontal, so I don't see how it could have had the ball valve in 1932.  I don't know if the non return was used in the 20's. It can only be a good thing...reducing crankcase pressure, reducing leaks and pumping losses.  Probably...but maybe Crankcase pressure helps to lubricate main bearings when you have total loss piling?

I just found a 1927 parts list. It gives 'part number 2028. Crankcase breather with disc and screws complete for all models'.  Did they have a steel disc rather than a ball?

Paul, that is a rare and sought after beastie indeed !

I’m not sure what the breather would be. Suggest you try Simon Grigson on vintagenorton.com - he might probably know.

I don’t ever recall seeing the parts list for the M25.
 

Hi Folks, sorry have only just seen this . . . very rarely dial in here, but nice to talk to you all.

FYI - the One Way Valve talked about here looks similar to the 1/4 BSP breather as shown above . . . but was only fitted from (if memory serves me right, from about 33/34 onwards - and to my knowledge, always above the left main bearing housings.  Crankcases before this time did not have that type of one way valve - I have a set of early Inter crankcases (about 32) which do not have the one way valve . . . but has provision for a screw in plug in the side wall of the crankcase just above where the one way valve was later fitted.

I am not an expert on 1920's engines - but I know a clack valve type breather (valve?) was fitted on CS1's (and I think OHV engines) in the late 20's.  This was normally at the top of the crankcase behind the barrel (if memory serves me right), and had a small steel shim plate held against the hole of the breather, with a spring above it - then a chromed brass plug holding the spring down and securing a banjo.  Actually if you look at my RacingNorton catalog you will see I actually had the spring for that valve manufactured and is for sale, but as of now (May '24) have not got round to machining the actual brass parts of the valve (although I did do drawings if memory serves me correctly).
And yes - I do manufacture the later (main bearing) one-way valve, and two types of the original breather union (as well as SOHC and OHV engine oil pipe unions . . . all can be found on my online catalog: www.RacingNorton.co.uk.

Chrs
Paul Norman