I am a new owner of a 1926 OHV 500 Norton. i want to check that the oil breather is correct as it has no ball or disc valve and simply vents via a pipe onto the primary chain. if anyone has a Model 18 or similar with the same breather I would love to know what it should be like.
crank case union
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Paul Norman sells this. No…
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?
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Thanks for the replies gents
The bike is a 1926/7 model 25 which has a semi dry sump system similar to the early CS1, not a total loss system.The breather is at the top front of the left hand crankcase unlike the later machines like the one using the valves made by Paul on the Racing Norton site. If the original was simply a through pipe like the one currently fitted and I fit a prv either ball or disc I’m sure the old girl will leak oil from everywhere due to the increased pressure. The pre ‘28model 18 has the same breather by the look of the parts book. I will send an email to Paul Norman and see if he has idea what the early ones were like. Any other help gratefully received. A photo would be great.
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1927 Model 25
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.
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Parts list.
Thanks for the reply Alan, I’ll send Simon a message. The model 25 is included in the 1927 Norton parts book, it doesn’t have its own list that I can find. Cheers, Paul
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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