The Marston Sunbeam Club & Register Forum

General Category => Technical Discussion Forum => Topic started by: VicYouel on August 04, 2015, 10:14:47 AM

Title: Breathers
Post by: VicYouel 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?

Title: Re: Breathers
Post by: iansoady 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!)
Title: Re: Breathers
Post by: phutton on August 05, 2015, 04:40:37 PM
Mine just has a flap - no spring! It seems to work ok...
Title: Re: Breathers
Post by: VicYouel 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
Title: Re: Breathers
Post by: iansoady 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.

(http://i43.photobucket.com/albums/e398/iansoady/bike/Sunbeam/lubrication/IMG_2191_zpsldt0kozo.jpg)


(http://i43.photobucket.com/albums/e398/iansoady/bike/Sunbeam/lubrication/IMG_2192_zpsvsuwnewi.jpg)
Title: Re: Breathers
Post by: singleminded 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
Title: Re: Breathers
Post by: iansoady on August 09, 2015, 11:03:42 AM
I guess a disc and spring would fit. I'll make a try when I get round to that part.
Title: Re: Breathers
Post by: wessex_man on August 10, 2015, 09:14:08 PM
Yes I think it should be a diaphragm disc and spring. A pipe is attached to the breather and normally vented on to the chain.
Title: Re: Breathers
Post by: VicYouel on August 10, 2015, 09:24:55 PM
Mine just has a flap - no spring! It seems to work ok...
Paul,

 I talked to Peter Woodward.... he believes that without the spring there is a danger the disc will block the outlet and therefore not function properly. He has measured a disc made from 7 thou shim as 0.535 inches diameter.

cheers

Vic
Title: Re: Breathers
Post by: VicYouel on August 11, 2015, 09:55:22 PM
Mine just has a flap - no spring! It seems to work ok...
Paul,

 I talked to Peter Woodward.... he believes that without the spring there is a danger the disc will block the outlet and therefore not function properly. He has measured a disc made from 7 thou shim as 0.535 inches diameter.

cheers

Paul,

Just chatted to Peter again.... actually the problem is not blocking but likely damage to the thin disc if you do not use a spring.

Vic

Vic
Title: Re: Breathers
Post by: AndyB on October 28, 2018, 05:07:05 PM
I lost the pipe from the breather on my '32 Lion 600, and it began to make loud whistling sounds, so I took off the mag drive / cam-chest so I could remove the breather and found just a tiny steel disc (1/4inch x 12thou) loose inside, no sign of a spring.
Should I use the measurements quoted by Peter Woodward to make a new disc, and does anyone know where I can source a suitable spring?
Edit - Photos added 29-10-18

Thanks
AndyB

[/quote]
Mine just has a flap - no spring! It seems to work ok...
[/quote]
Paul,

 I talked to Peter Woodward.... he believes that without the spring there is a danger the disc will block the outlet and therefore not function properly. He has measured a disc made from 7 thou shim as 0.535 inches diameter.

cheers

Paul,

Just chatted to Peter again.... actually the problem is not blocking but likely damage to the thin disc if you do not use a spring.

Vic

Vic
[/quote]
[/quote]
Title: Re: Breathers
Post by: kbryt on October 28, 2018, 08:11:40 PM
I think the breather discs from AMC singles do the job; no spring in those though
Title: Re: Breathers
Post by: AndyB on October 29, 2018, 10:08:10 AM
Thanks kbryt - it looks like they are available from AJS & Matchless owners club - part number 000835 - however they only sell to members, which I am not.  :(
Title: Re: Breathers
Post by: kbryt on October 29, 2018, 10:12:53 AM
PM me  I think I can find you one, and as my 'beam is on the bench I can double check it before hand.
Title: Re: Breathers
Post by: klaudius on February 02, 2019, 05:08:40 PM
Hello. Please indulgence with my bad English. I have already had the feathers that are being searched done. Original were made of 0.3 mm material. I have also made the addition of 0.4 mm. Funkcion tested for 3000 km on my 600 SV 1932.  If you need such a spring say which thickness is 0.3 or 0.4 mm. greeting
Claudius
Title: Re: Breathers
Post by: AndyB on February 03, 2019, 04:40:12 PM
Thank you Claudius, I have re-assembled the breather with a disc kindly supplied by Kbryt, and a spring obtained via Ebay (from China!), and it seems to work OK so far. I haven't yet had the opportunity to run it for long enough to be certain, but I'll post an update in due course. My springs are slightly longer than the ones you show, but will hopefully do the trick...
Andy
Title: Re: Breathers
Post by: Tom Snow on February 05, 2019, 11:26:02 AM
Hello, Klaudius is right on the money, there should be a hair spring holding the disc in place so the gases from the crankcase can escape but not let air back in creating a partial vacuum in the crankcase and keeping the oil in. I have an original spring new and unused which I intend to have reproduced, if you would like some for the club Vic just let me know.

Regards,

Tom.
Title: Re: Breathers
Post by: phutton on February 10, 2019, 01:16:42 PM
I'll have one!

P.
Title: Re: Breathers
Post by: VicYouel on February 11, 2019, 04:28:21 PM
Tom
Yesplease I would like to add this item to our shop..... let me know price etc.....
Cheerio for now
Vic
Title: Re: Breathers
Post by: Tom Snow on May 06, 2019, 02:10:07 PM
Good day All,

The spring and disc is now available from the new spares scheme an a very reasonable £5 I believe.

Regards,

Tom.
Title: Re: Breathers
Post by: VicYouel on May 13, 2019, 09:04:10 AM
Thanks much Tom!!
Vic