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Author Topic: Breathers  (Read 3702 times)

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singleminded

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Re: Breathers
« Reply #6 on: August 09, 2015, 10:42:30 AM »
My 1932 9A has a similar looking arrangement.It used to have a disc and light spring in it..One day it started whistling and on inspection I found that both had disappeared???.John

iansoady

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Re: Breathers
« Reply #5 on: August 07, 2015, 03:48:18 PM »
As I'm now working my way forward I have the breather on my Model 10 in pieces. I appreciate:

1. It (like everything else on this model) is probably different to what others have and

2. I have no idea whether it's original.

It consists of 2 parts threaded together as in the (not very good) photos. The long spigot extends into the timing chest from a position at about 10:30 pm. It has what looks like a seat for a ball bearing or similar. The other part could hold a light spring. There's no sign of any flap or other internals.

The best way forward for this may be a ball as per Norton singles as I mentioned earlier.




Ian
1931 Model 10
1993 Honda CB400 Super Four

VicYouel

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Re: Breathers
« Reply #4 on: August 07, 2015, 10:23:11 AM »
Annoyingly my 1932 parts list does not specify the parts of the breather..... only the part number for the assembly

phutton

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Re: Breathers
« Reply #3 on: August 05, 2015, 04:40:37 PM »
Mine just has a flap - no spring! It seems to work ok...

iansoady

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Re: Breathers
« Reply #2 on: August 04, 2015, 01:54:10 PM »
Norton singles had a simple device that was just a ball bearing on a seat (with no spring). Crankcase pressure blew it off the seat and allowed (oily) air past it then as the piston rose atmospheric pressure pushed it back on. The whole thing screwed into the drive side crankcase behind the primary chaincase. It had something like a 1/4" gas thread from memory.

It shouldn't be too hard to make something similar for the Sunbeam although I'm not familiar with the working (or not) of the original (yet!)
Ian
1931 Model 10
1993 Honda CB400 Super Four

VicYouel

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Breathers
« Reply #1 on: August 04, 2015, 10:14:47 AM »
Another member asked me today about breathers on the early thirties models (and probably late twenties too).  Unless they are working properly and generating a partial vacuum in the crankcase  there will be lots of excess oiling problems.

The breather is almost impossible  to access behind the magneto chaincase; the best way of checking is to attach a balloon on  the breather pipe to see whether it blows up. unless you go to t he trouble to remove it and attempt a suck/blow test.

The breather consists of a tiny light metal flap with a fine spring.... both corrode and fail over the years.

Does anybody out there know of a useful after market one way breather valve that can be utilised and easily disguised?