dumb question

Needing appreciate your inventiveness but ain't smart enough yet to understand your system purpose on how it can. Fresh air intake to crankcase requires less blow by pressure than ambient or fresh air prevented entry same as normal Nortons. As blow by pressure and oil pumped to catch tank what keeps oil filling it to pour out its vent and instead of returned to tank? I don't see a purpose for the float switch nor what it swtiches in your set up except maybe the air vent but then why vent catch tank anyway? I need some tutoring as nothing above makes sense to me yet I've plumbed Peel's OIF sealed from ambian thinking I did understand Norton flows and pressure gradients. I assume you did not leave off tank to engine oil path in real life. Half calling you out on this but other half happy to learn more and see such interesting DIY one in a row gizmos. Would like for you to review my own 1-in-row as pensive it could either pop a seam of crush inward giving the gun.

Ta.

Ta.

Thanx for the second round of explaining. I got it now and smarter for it. Spraghrope cycles fictional special features should of been so functional. Btw oil pumps of about all type better dang sure pump air along with oil but no air as needing set up is optimal. Rest of us get by with just adequate good enough. The elite race engine just use more and bigger regular oil pump to pull low vapor pressure down below ambient.

Ta.

Did not mean to imply Norton sizd pumps could lower blow by pressure just that oil pumps can pump fairly aerated oil and if enough of em pumping they can pump down to approach vacuum. You may have an alert point that Norton pumps aren't sized to pump enough of their aerated oil when on cam rpms so Combat famous wet sump on the fly till over flowing up breather hose. If so another reason to say our Commandos are allergic to much rpms.

I run a small plastic bottle (catch can) with vent hole coming off of the breather on my 73 oil tank. After about a thousand miles on my bike since rebuild there is only a few drops of oil in the bottle. Seems like this set up is working just fine.

On my 850 I have one of Jim's sump valves. It seems to empty the sump build upon start up.
After I put the valve in I put the tank vent line over the side of the bike just so I could see
how much oil was coming out.
None and I suspect because I tend to keep the oil level in the tank to the very tip of the
dipstick giving me more room atop the oil for vapor.
So despite the fact that the damn think leaks at the primary crank seal it seems to work.
No oil leaks elsewhere at all.

As my old practical instructor used to say when I started my apprenticeship:

"There are no silly (dumb) questions only silly mistakes".

A Friend vented his velo into the oil tank, which is not the Original design. After a few miles the tank neck was white with "mayo" he thought the problem was air/oil emulsion , After trying to tell him it's a by product of combustion ,we routed a 57 inch of 1/2 bore pipe to the rear wheel. the case blow by was seen to exit as a thick cream after a few miles.
My question was/is does the Norton pump with its 100% return of case gas have the same effect? ie pumping these combustion gas's into the oil tank?
I have known for 50 years the general idea is double the pump return gears . but for years wonder why..at the end of the day if the pump is feeding at eg 1 pint a minute then only 1 pint a minute can be pumped back?
So on a "dry start" up the pump is pumping nothing , then when some falls into the sump ,that is sucked up ..then sucks gas that is escaping past the engine parts. This is not hard to see?

hobot said:

Did not mean to imply Norton sizd pumps could lower blow by pressure just that oil pumps can pump fairly aerated oil and if enough of em pumping they can pump down to approach vacuum. You may have an alert point that Norton pumps aren't sized to pump enough of their aerated oil when on cam rpms so Combat famous wet sump on the fly till over flowing up breather hose. If so another reason to say our Commandos are allergic to much rpms.

Click to expand...

Hi John. Don't you realise that when these engines are stopped, all the oil built up in the head etc flow to the bottom. It is undesirable to have the flywheel thrash through a load of oil so that is why the return pump always has a higher capacity than the pressure pump. They may not always be 2:1 though. See my previous comment.
None of my Commandos have any problems with salad dressing, maybe because I always ride for 20 miles or more when I use them. Both the 71 750 and the 74 850 run the standard type breathers they originally had although I have fitted a Jowet twin reed type vale in the return line on the 850. Both still relieve through into the air filter [ and although the filters get oil wet on the bottom, it never has been a problem.]
Dereck.

I strongly recommend you don't alter the return pump. It is not doing any harm the way it is [ hence the comment "don't reinvent the wheel Mac" ]

Trying to understand as I go. Velo example is problematic to comprehend so I didn't learn from it. I could see if oil tank not warmed up to operating temp then vented blowy puffs with some suck back returns might have time enough to cool and condense moisture to act as emulsify agent. Long hoses are like moonshiner worms and would take a while long to come to temp it it ever did. Still i've seen plenty of cycle oil tank vent hose or just straight out hoses and they only showed black oil hints no creamyness.

My cdo's and my buddy returns oil with visible bubbles on scale seen in cokes via baffle that spills on tank walls to see oil lay with bubbles carried an inch+ down then pop leaving mist size bubble on oil surface but so light it stays on top to fizz out before reaching tank exit to pump again.

Needing got a point to hang on, Apparently Norton pumps are not able to pump all the blowby out with aerated oil so need extra case vent or pressurizes for oil weeps. Most blowby gases will not enter oil so majority must be expelled in vapor state not mixed in oil. Old Italian cycle had large ship like funnel vents to keep ambiant pressure and lower pumping loss.

Needing maybe you could experiment with an exhaust extractor,aka, Eductor, for active lowering pressure, maybe to point most the air just boils right out the oil so nil to separate before pumped.