Sump Breather Hose Delete?

[sp838]

I know these questions can get people riled up, but I'm curious to know if anyone has a good explanation for what the small sump breather hose does and if it is really all that necessary. Not talking about the big crank case breather, but rather the smaller hose on the back of the sump, that connects to the left of the drain plug. Seems like the crank breather should be enough to handle breathing duties, no? I would really love to get rid of it, if it's not really contributing much to the overall effort.

[Camn]

Isn’t it so that the breathing system of V11 is among the best in Guzzis? Oil fumes travel with the ”breathing air” along the large breather pipe up, to the upper part of the (spine) frame. The frame tube is hollow, and works as a liquifier. The main part of the small oil drops in the oil fumes are separated.  The air, is directed to the suction box and from there, to motor with the intake air (a part of this oil stays on the bottom of the suction box). The separated oil flows with gravity inside the main frame tube to the bottom of it, and from there, along this small pipe (which was the quesiton), back to the sump.

 

But why there is no ”one way valve” at the breather pipe outlet on V11? Many other models with the 2V big block do have it… maybe because of the breathing system itself...

[jchayes]

Yeah, that ain't a "breather," that's the oil return line from the crankcase blow-by oil/vapor separator.

[sp838]

Right, it's the oil return for the crank breather. So the question is, how much oil comes back down from there? If it's negligible, it could be capped off. Just top oil off every so often, and then drain it when doing oil changes, could be possible. If it doesn't affect the breathing of the engine, and if lots and lots of oil doesn't get spat up in there, shouldn't be an issue deleting it right? 

[MartyNZ]

Right, it's the oil return for the crank breather. So the question is, how much oil comes back down from there? If it's negligible, it could be capped off. Just top oil off every so often, and then drain it when doing oil changes, could be possible. If it doesn't affect the breathing of the engine, and if lots and lots of oil doesn't get spat up in there, shouldn't be an issue deleting it right?

 

You could prove to yourself whether you need the oil return hose by putting the hose into a temporary collector bottle, then going for a fast run. (after blanking off the the sump fitting of course).

A split in my old breather hose meant two drips of oil out the bottom of the clutch housing everywhere I stopped, and probably faster drip rate with the engine running. Even with the split, I think most oil vapor was still getting up into the spine, and then to either the airbox or the sump.

I think that this probably means that the return oil flow is more than negligible, depending on many things like power setting, rpm, oil temp/quality/quantity, Roper plate installed, piston ring wear...

If you try it, can you let us know what you find out?

[GuzziMoto]

In my experience there is a fair amount of oil that is collected and returned to the sump. I did run that for a time into a catch bottle on my Daytona. I switched it back after a while as it was a fair amount of oil.

It is actually a well designed system as long as it is in working order. My issue with the Daytona was that the frame was not oil tight, so it leaked. I ran the breather to a catch bottle to stop it dripping out of the frame. After a while I decided that was too much oil and I sealed the frame so I could route the breather back into the frame. The stock set up works very well and does not cause issues, unless something is amiss. I would not change it. It isn't harming anything and it did catch a lot of oil on my Daytona.

[sp838]

I'm thinking I might install a check valve on the crank breather, then replace the return line with a length of clear hose with a plug in it. Then I can have a visual on how much is being returned. I can always revert to stock if it's looking like there's a lot of oil that wants to come back. I do have a Roper plate installed fwiw.

[Scud]

It's a lot of oil.  I recently left the breather hose disconnected by accident.  Rode 4 miles - oil everywhere.  It was a perfect topper to my clutch frustrations (now solved).

[Lucky Phil]

I'm thinking I might install a check valve on the crank breather, then replace the return line with a length of clear hose with a plug in it. Then I can have a visual on how much is being returned. I can always revert to stock if it's looking like there's a lot of oil that wants to come back. I do have a Roper plate installed fwiw.

Life a bit boring lately?

 

Ciao

[sp838]

It's a lot of oil. I recently left the breather hose disconnected by accident. Rode 4 miles - oil everywhere. It was a perfect topper to my clutch frustrations (now solved).

Hmm, good to know. Theory is that a check valve in the crank breather can reduce positive pressure in the bottom end and thereby among other benefits reduce how much air/oil gets spat out. Ducati, BMW, even Harley uses them, and have been for quite a while. The new Panigale goes so far as to having a pump in the crankcase to keep it under negative pressure. Methinks it can help. They aren't expensive, either.

[sp838]

Life a bit boring lately?

 

Ciao

Unfortunately not. Way too much on my mind, this sort of thing helps with that

[swooshdave]

 

It's a lot of oil. I recently left the breather hose disconnected by accident. Rode 4 miles - oil everywhere. It was a perfect topper to my clutch frustrations (now solved).

Hmm, good to know. Theory is that a check valve in the crank breather can reduce positive pressure in the bottom end and thereby among other benefits reduce how much air/oil gets spat out. Ducati, BMW, even Harley uses them, and have been for quite a while. The new Panigale goes so far as to having a pump in the crankcase to keep it under negative pressure. Methinks it can help. They aren't expensive, either.

 

 

Reed valve breathers are the simplest way to reduce the crankcase pressure.

[Scud]

 

Life a bit boring lately?

 

Ciao

Unfortunately not. Way too much on my mind, this sort of thing helps with that

 

 

Weirdly, I understand that. When things get really complicated at work, I enjoy the mental retreat to the relatively simple turning of wrenches.

[sp838]

Reed valve breathers are the simplest way to reduce the crankcase pressure.

 

I have been advised by esteemed sources as well as from some forum crawling that power brake booster check valves work well.

[docc]

Did not pre-V11 big blocks have a check valve in the main vent? Is not the same thing?