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Crankcase breather slot

Submitted by hans_eberlein on Saturday, 13 February, 2016 - 00:00
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Singles

Hello all,

I wish to know if the slot in the left half crankcase of my Norton 18 1947 should have a sponge in it, or just let it free?

I saw at RGM a sponge, but not sure if for my Norton.

Another question: At the rear of the crankcase mouth is provided a hole for lubrication of the cylinder wall.

As I bought the bike, the cylinder was fully distorted, so, no traces of where the hole was.

How should the cylinder wall be drilled: slanted upright, or up and for in a right angle?

Thanks in advance,

Hans from Chile

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Submitted by svein_marken on Monday, 15 February, 2016 - 00:01

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Hello, I have owned some singles and I have never seen any sponge on any of the engines I have opened,and the cylinderlubricationhole are slanted upright. I am not sure about you need this lubrication at all. This have been blocked on some engines I have seen,specially if the cylinder is resleeved.

Regards from Svein in Norway.

Submitted by hans_eberlein on Tuesday, 16 February, 2016 - 00:00

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Hi Sven,

Thank you for the info. It is very helpful for me.

It seems to be that my Norton is the only one of this model in the NOC?

Regards,

Hans from Chile.

Submitted by richard_payne on Tuesday, 16 February, 2016 - 00:02

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Hans, I don't think that it's fair to assume that the NOC is packed with owners of pre-'48 singles who work on their own engines and have the time and inclination to scroll up and down internet forums in the hope of answering queries.

Anyone answering has to be certain of their information or say 'I don't know...'

There is no mention of any packing material in the crankcase groove in the 1935, 1937, 1938 or WD Spare Parts Lists. My understanding is that this would be counter-productive as the slot is simply a scraper and catch area for any oil that has made its way past the twin main bearings, ensuring that it then drains by dribbling down the back of the primary chaincase rather than being forced into the chaincase where it would build up and eventually cause clutch slipping problems etc...but I'm not an engineer. I could be wrong.

The rear cylinder lubrication hole is simply angled from the base flange and it is normally recommended to re-drill it if fitting a liner. It must have been put there for a purpose. If there is a problem with over-lubrication of the cylinder wall, it can be regulated by means of the screw at the rear of the timing cover.

Submitted by hans_eberlein on Tuesday, 16 February, 2016 - 00:03

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Thank you Richard for the help.

As an owner of a Norton 18 1947, I joined the NOC recently as a logical reason: It is the main source of information, as can be read in the advertisements of the classic bikes magazines, being the first offer the Technical Help.

My aim is to form a Classic British Bike Museum here in Chile, where no experts in Norton, no parts and no autojumbles can be found.

Added to that, particularly the 1947 production was mainly for overseas, whose owners were not so interested in keep manuals or any info. Needless to say that spare parts list are unillustrated.

Attached a photograph with the timing cover which isn?t provided with a oil flow regulating screw. Only a pressure valve can be set.

In those days developing went very fast, making confusion about spares and restoration. ?Really a challenge!

Finally, I?m proud to own classic british bikes, and hope further to show my bikes in a decent running conditions.

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Submitted by hans_eberlein on Monday, 22 February, 2016 - 00:00

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Hello all,

Asking RGM about that, Mr. Lawrence McDowell told me that nothing should be put into the breather slot, acting it as a timed breather.

Thank you anyways for those who helped me with the question.

Regards,

Hans from Chile.

Submitted by hans_eberlein on Monday, 22 February, 2016 - 00:04

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Hello all,

Asking RGM about that, Mr. Lawrence McDowell told me that nothing should be put into the breather slot, acting it as a timed breather.

Thank you anyways for those who helped me with the question.

Regards,

Hans from Chile.

Submitted by paul_knapp on Tuesday, 23 February, 2016 - 00:00

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Hi Hans, re your original question, (part two), the oil hole in the back of the cylinder is just a small hole, I can't remember the size but I think around 1.5mm. I have blocked mine off. The only thing to watch if you re drill it, is to measure before hand the position where it isin relation to the oil control ring in the piston. I know of one instance where the hole was re drilled after a re sleeve and it exitedabovethe oil ring, and the owner wondered whythe engine continually burned oil. One he discovered the problem, and blocked off the hole and relocating it lower down the bore, the smoke stopped.

Cheers,

Paul

Submitted by hans_eberlein on Thursday, 3 March, 2016 - 00:00

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Hi Paul,

Thank you for the info. I drilled the sleeve in such manner that it is a continuity of the slanted hole at the crankcase mouth, emerging inside the sleeve in so a position that it reaches the centre of the oil ring when the piston is at BDC.

I assume then, no worry about excess of oil consumption. I also noticed that the oil restriction is just below the surface of the timing cover.

Sealing of cylinder-crankcase oil passage should be not a problem as a paper gasket is provided, but: what about crankcase-timing cover?

Using sealant is, I think, a bit risky, having preferred milling a small 8 mm. recess at the timing cover and put a small o-ring, leaving a sealant only for the rest of the cover.

Hans from Chile.

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Submitted by paul_knapp on Friday, 4 March, 2016 - 00:00

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Hans, nice job with the 'O' ring'. To block off the barrel oil feed, I didn't cut the hole in base gasket. I also use Loctite Master Gasket 515 on the crank case and critical areas around oil ways, as any excess will wash off and dissolve in the oil internally.

That timed breather in the drive side case will emit a very small amount of oil, which can be seen gathering on the bottom of the case. I often wondered where it came from till I stripped the engine and found the timed breather slot.

Paul

 



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