72 Eldo wont run anymore

[Antietam Classic Cycle]

I checked the oil level today and it was bone dry. It seems i completely lost all the oil during the short test drive.

I removed the oil pan and yes there was nearly nothing left. Luckily there was absolutely no metal in the oil pan.

I refilled the engine with 2.5 liters of the same oil i was using during last season - Motul 20W-50 mineral classic oil - which ist enough for exactly half of the dip stick.

Drove the same tour as the day before but stopping and checking the oil breather athmosphere hose every 3-5 minutes. At first everything was fine but after about 10 minutes the breather started pumping out the oil. Literally pumping like you cut an artery. Huge squirts every 2 seconds repeatedly.
Headed home instantly using the side roads and when i came home I nearly lost 1.5 liters fresh oil!!!!!

Its a new breather from Stein-Dinse
https://www.stein-dinse.com/en/moto-guzzi-oil-condenser-v7-700-spezial-850-gt/item-2-1050679-12155701_.Z.html
The old breather worked fine with that oil.
Is that now the second faulty SD part within days or ist the 20W-50 too thin for that after market breather?? Could it bei that it sucks my whole engine dry even in idle with 1200 rpm!?

I've used the same breather on a number of bikes and have never had a problem. Why did you replace the breather if the old one worked fine? Is there another check valve in the pipe coming from the engine to the breather, such as one like this?

[John A]

On later models with the breather in the frame there was a scenario where it would pump out a quart in a heartbeat at road speed. What would happen is the ball valve, which replaced the earlier flapper valve in the breather box and Charlie has pictured above,could close off completely causing the crankcase to pressurize and pump oil out of the external breather drain. It pushes the oil up the internal breather drain in the crankcase which has its end below the oil level. When the oil level gets below the drain tube opening, it quits. That was fixed with the ball valve, which sits in the large breather tube at the top rear of the engine, being changed. Instead of having a round hole that the ball could close off the new ones have a square outlet hole the ball cannot close completely.

[Tom H]

John A, thanks for that explanation. So if his flapper is stuck shut, the oil would come up the line that should return the oil to the crankcase.

Thank you,
Tom

[jacksonracingcomau]

I too bought a brand new old type breather box , not from SD but the identical part (no rocker breathers, just in and drain + outlet )
This went on my Luddite 1100 cali motor into early Tonti

Amazingly, it did immediately fail , maybe not quite as quickly as op’s but certainly within weeks. I removed the stuck flapper valve and all’s been well for 50k miles.
Yes, Tom, when blocked , the oil goes “up” the drain pipe and out via box outlet. Messy

Also the latest pcv valve has a rubber seal so it does seal 100% and cannot rust itself together (some great pics of this on here over the years, rust in sump led to one discovery )
These in all my BB’s now but note they come unassembled , takes a minute to get rubber seal on properly

I have only seen the stuck flapper once other than my new old box and that was on a T3, 100.000 miles without issue suddenly chucked it’s oil out. Offending flapper removed. When I built my V700 I cut box open, removed flapper before even running it, like Charlie I’ve gone 40 years without seeing the failure but having now seen it twice, no reason at all  to see it again.

One other way they can pump oil is when drain pipe banjo has been cut so is not under the oil level, it is then acting as another breather, not a drain. The crankcase pressure up the pipe forces the oil out.
That one took a bit of working out , I made an external drain under oil level and routed hose to that. Fixed problem

System as Carcano designed is correct, only tweak In nearly 60 years would be ditch the flapper and use a rubber seal on pcv valve

[DodgeBoy]

Why did you replace the breather if the old one worked fine? Is there another check valve in the pipe coming from the engine to the breather, such as one like this?

The old one was really, really rusty and looked bad. When i had the coil and stuff out i saw SD had that breather and thought why not changing it because its only 3 hoses so easy...but now...
No, there is no such check valve in the hose.

One other way they can pump oil is when drain pipe banjo has been cut so is not under the oil level, it is then acting as another breather, not a drain. The crankcase pressure up the pipe forces the oil out.
That one took a bit of working out , I made an external drain under oil level and routed hose to that. Fixed problem

Sorry, i am not quite sure if i understand what you mean... There was nothing modified at least not by me If thats what you mean?

What would happen If one of the two cylinder head oil lines are plugged? I mean the upper ones with the hollow screw.

When i installed the new breather i mentioned that the thinner oil return tube (pos 14) where the smaller hose from the breather comes on was maybe a bit loose. I think the upper clamp which holds the tube inside in place might be a bit loose but what would happen If that tube disconnects from the hollow bolt inside the case (pos 16)or gets damaged?



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So If I understand you guys correctly another way would be deactivating the flapper inside the breather (or if is allready broken) and Install that check valve in the small hose?

[Don G]

Check valve goes in the big hose, actually fits into the breather pipe. I see that you had the cylinder heads rebuilt, did you do anything with the cylinder bores and rings by any chance?  DonG

[John A]

John A, thanks for that explanation. So if his flapper is stuck shut, the oil would come up the line that should return the oil to the crankcase.

Thank you,
Tom

I pulled the heads twice before I figured that one out. Going home from an Oklahoma rally, early’80s , I dumped a quart of oil on my wife on her Ambassador at 70 mph. Luckily I had re routed the drain from the air box to overboard so it didn’t hurt the engine but I didn’t know that for a couple weeks. It was on a Cal2, just out of warranty so I fumbled through it myself.

[DodgeBoy]

Check valve goes in the big hose, actually fits into the breather pipe. I see that you had the cylinder heads rebuilt, did you do anything with the cylinder bores and rings by any chance?  DonG

The cylinders are stock T3 ones but they are the same as last season. I inspected the rings once while the bike was without heads and reinstalled the old ones again since they looked good. I allready checked compression on both cylinders 10,3 / 10,5 bar cold which should be fine.
The breather starts pumping the oil as soon as the bike is on full operating temperature it seems. It wont do it cold or half warm.