Crank Case Breather

klaudius · July 13, 2019, 12:47:55 PM

Hello. The oil pumps Dry Suppf Pumps 1932 and the former 1929 are in themselves two different systems. Comparing them makes little sense. The 1932 models are my opinion not dry put in the state. As long as it is original (without oil tap after oil tank exit), the oil runs out after a certain life ... The whole has certainly worked 100% only theoretically on paper well. The venting with small plates and spring is a good construct. It could happen, however, that the spring twisted too easily and twisted in the seal plate. I've already blessed that. the effect is equal to 0. I have built the spring slightly different. See photo. The conical side to mouth. The original wire thickness is 0.3 mm. This is how all 350-500 motors work. Experimentally used also 0.4 mm wire thickness in the 600 SV and OHV. Funkcioniert very well and lasts a little longer ... Building special tools to get to the bottom is an advantage. Bad spot Sunbeam could hardly choose ... Greetings Klaudius. Sorry for my english

wessex_man · July 11, 2019, 06:15:41 PM

The oil has to go somewhere. In the total loss system a certain amount will lubricate the bore and get expelled by the exhaust. Otherwise it will just gather in the crankcase, find it's level and exit via the breather. A reason not to fit oil scraper rings on the piston. I drain mine at the start of the season as the bore is good and it can gather quite a bit. Too much oil in the crank causes the flywheel to drag and makes starting less easy and a sign to drain the crankcases.

Also on the flatters we have had the oil siphon from the oil tank go and fill up the crank cases to the mains. Solution open the sight gauge cap in between use, remembering to tighten up again in use, else you will not get oil circulating.

Sunbeam must have been aware of all this and brought out the circulating oil models where the oil is scavanged at twice the rate of the delivery. So when it sumped the oil was returned quickly. When in daily use it was probably never noticed.

rakehill · July 11, 2019, 08:28:14 AM

Thanks again for your further thoughts, I've now removed and tested the breather and I can see that the valve opens and closes ok. I've also drained the crank case of oil. I'm not sure how much oil should have been in there but it didn't strike me as being a great quantity. When I started the bike it smoked less and no oil came through the breather. Would this be due to the oil being removed from the crank case?

Rick Parkington · July 10, 2019, 11:14:09 AM

Hmmm, fair comment - breathers pass a lot of moist air so I guess corrosion is another big problem.
Cheers R

singleminded · July 10, 2019, 08:27:38 AM

In my case Rick, it just disintegrated. Spring and all $:-\$

Rick Parkington · July 10, 2019, 12:54:01 AM

I think I would check the breather first, Rakehill, as it is the easier job. I'm assuming it screws into the timing chest and is (hopefully!) fairly easily removed. You just need to check it acts as a valve by blowing and sucking, you should be able to blow through from the crankcase side but it should flap shut if you try to suck back through it. It's easy for these valves to gum up with burnt oil or be held open by some piece of debris from the engine and simply washing out in petrol might cure it.
As you say a total loss engine can be expected to smoke and if your pump setting doesn't usually cause over oiling it's unlikely to be a problem now although thinking about it, have you checked the quantity of oil in the sump? it might be worth draining to find out.
Hopefully you aren't suffering my problem of an internal tank leak, I had about a pint of very diluted oil in my sump. The petrol having thinned it so much, I guess it got through much faster than usual.
Cheers Rick

rakehill · July 09, 2019, 10:03:29 PM

Hi All, and thank you for your thoughts. My bike is a total loss system and I have set the oiling rate at the sight feed on the Best and Lloyd pump to a fairly slow drip rate. From what has been said it seems likely that the problem is due to wear in the cylinder or the valve on the breather. I've had the bike for quite a few years and have never removed the cylinder. It is 350cc side valve which starts easily and pulls ok but does give out some smoke but I'd thought that was quite normal for a machine like that. Would I be best to check the breather first snd if so how should I go about it? Any thoughts would be really appreciated

Rick Parkington · July 07, 2019, 07:56:59 PM

No, you're quite right Vic. I believe modern engines run at atmospheric pressure - obviously pressure or vacuum is a resitance the engine uses power to overcome - but old engines definitely relied on running a vacuum to keep oil tight and that's why the timed breathers came about.
My 9A has its original breather and works fine - it was just the wet sumping when standing that caused me trouble.
What bothers me slightly is how come my flat tank Model 9 breather is at the 8 o'clock position on the timing chest? You'd think the oil would pour out but it doesn't seem to. 1929-on were on top of the timing chest which seems far more sensible.
Anyway, back to work, I'm in soldering mode having missed a gear on the '28 at the Crystal Palace day last month. An over-revved rocker actuated by 30/60 cams hit the bottom of the tank, causing a leak between the fuel and oil compartments - thanks to Winold and Odling who said there's a blank space between the two tanks...but take my word there isn't on my tank - so I have mostly spent the past umpteen evenings trying to solder it up via the oil tank cap hole...
It's booked in for a romp at Mallory Park 1000 Bikes next weekend; last year it tore round brilliantly so wish me luck!!
Cheers R

VicYouel · July 07, 2019, 05:17:15 PM

Rick,
There is a breather kit (a skinny piece of steel and a spring copied from an original) that can be fitted to the breather behind the mag chain case that feeds the rear chain. Available on the club shop. Without this I believe insufficient vacuum will be maintained in the crankcase.... but then I am probably wrong but that breather is there for a reason. Certainly fits your 1932 model 9 but not sure what earlier models used. It is pretty annoying to fit though!
Vic

Rick Parkington · July 07, 2019, 04:43:45 PM

Wet sumping is certainly a likely cause with a circulating system - in theory the Sunbeam telltale should cut the oil feed supply until the engine is started but I was told that the since the telltale is o the outlet of the pump, the pump itself is still subject to the full head of pressure from the oil tank and that can cause oil to migrate from the feed side of the pump, via wear in the spindle housing, to the scavenge side where it trickles down the scavenge line back into the crankcase.
On my '32 9A I attempted to cure this by making a ball valve in the scavenge line. The ball operates under its own weight with no spring so that oil pressure can easily lift it but in theory gravity seals it when the engine is at rest. It didn't seem completely successful though so I did what everybody else suggested and soldered up the Number 1 position on the tap and turned it off.
But if it's a Best and Lloyd/Pilgrim type setup presumably that's total loss and I guess there is a tap anyway? In that case maybe check that the breather valve is operating. Although not all engines have a timed/valve breather, it seems those that do can build up excess pressure when the valve doesn't close properly.
Breathers are not so much there to cope with the descending piston because there should be an equilibrium between piton up and piston down, the breather is primarily there to get rid of excess pressure caused by blowby at the piston rings and if it doesn't close, this blowby added to the fact that it i inhaling as much as it exhales seems to create a build in pressure that leads to leakage.
So if wet sumping isn't the cause I would suspect a problem with the valve not operating correctly or maybe excess pressurisation from worn rings or bore.
Cheers Rick

Rennmaschine1930 · July 03, 2019, 11:41:48 PM

Did you drain the sump before riding? A lot of oil can get into the case by gravity over a short period of time. Despite numerous adjustments, good mechanicals, my 1930 ohv will sump within a week of inoperation. IMHO, You have to drain it first or you'll end up wearing it.

rakehill · July 01, 2019, 01:20:53 PM

I enjoyed a great ride on Saturday at the Annual Rally. My bike a 1929 Model 2 350cc side valve went really well, without any problems on route. At the end however I noticed that one side of the rear tyre was coated in oil as was the adjacent frame and other items. It seems to me that I'm getting too much oil onto the rear chain from the crank case breather. The surplus oil is the being flung off the chain all over the place. Does anyone know how I can control the oil flow or does it mean that there is something wrong with the oiling into the crank case. The bike has the Best and Lloyd oil feed pump which is a sight feed similar to a pilgrim pump. I have it set on a fairly slow drip feed.