QUOTA 1100ES: why would you run a breather tube from the filler cap of the rear drive?

[p6x]

I believe older Le Mans have that identical rear drive transmission; including the Daytona RS?

The Quota 1100ES that I looked at yesterday had a breather tube running from the "B" filler cap. The filler cap was modified to include a lipped nipple onto which a rubber hose was connected and running around the frame, held by plastic straps, and opened to the ground.

Clearly an oil breather;

Why would you need this? the rear drive is filled up until oil comes out of "A".

Is there a known issue with this rear drive transmission that would require an oil breather?

 

[Chuck]

It doesn't hurt anything. I've never used the "A" plug. It's easy enough to booger the threads up, so I just drain and measure.

[p6x]

1 hour ago, Chuck said:

It doesn't hurt anything. I've never used the "A" plug. It's easy enough to booger the threads up, so I just drain and measure.

it hurts my view.... having a rubber hose that runs alongside the frame, clearly artisan looking and anchored with plastic ties. Sure, you can fill up using the A, or B plug, and an oil syringe. But why would you need a breather tube?

[docc]

Our V11 LeMans/Sports have an elegant breather vent on both the reardrive and the gearbox.

Why not add one to your Quota reardrive and loose the "artisan" solution?

 

[80CX100]

1 hour ago, p6x said:

 But why would you need a breather tube?

There have been reports that when fresh gear oil is put in the rear drive unit, as the fluid & air get hot & expands,it can be enough to blow seals over time;

That's why some people recommend burping the rear end shortly after the first good heat cycle.(I do it out of habit)

A vent cap or tube precludes the need for "burping"

[gstallons]

A vented system will keep the rear end at a constant ":pressure" and you will not have TROUBLE

[gstallons]

1 hour ago, docc said:

Our V11 LeMans/Sports have an elegant breather vent on both the reardrive and the gearbox.

Why not add one to your Quota reardrive and loose the "artisan" solution?

 

Did you finally get your rear end to not leak ?

[p6x]

1 hour ago, docc said:

Our V11 LeMans/Sports have an elegant breather vent on both the reardrive and the gearbox.

Why not add one to your Quota reardrive and loose the "artisan" solution?

 

Is this like a safety valve?

Interesting; I was unaware there was a pressure relief system where there is an air gap. I mean, if the full drive was filled up to the brim, then it would make sense. But air is compressible. PVT law (pressure, volume, temperature).

[p6x]

36 minutes ago, 80CX100 said:

There have been reports that when fresh gear oil is put in the rear drive unit, as the fluid & air get hot & expands,it can be enough to blow seals over time;

That's why some people recommend burping the rear end shortly after the first good heat cycle.(I do it out of habit)

A vent cap or tube precludes the need for "burping"

The air gap should cushion any pressure increase. A compensation system. Of course, if you put too much oil, you may exceed what the seal can withstand. But I can see that a safety valve is better.

 

[pete roper]

One thing being overlooked here is that the various bevelboxes are different and most 'Vent' differently.

On Loops, Tonti's and the Quota the pinion and its bearings aren't sealed. This means that theoretically the air in the box will vent through the bearings and into the swingarm and thence through the splines of the shaft and universal joint into the UJ housing where any 'Pressure' will simply cause the boot between the swingarm and gearbox to swell a bit. There is also that the extra volume of the swingarm etc. means that the pressure rise is proportionally low. We'll come back to this.

On the early Spineframes, Daytonas, Sport 1100's and Centy's what was essentially the same bevelbox was used but due to the shaft not being enclosed the pinion was sealed. On these boxes though the factory never fitted a breather and consequently seal failures due to pressurisation issues are fairly common, not helped by the sealing surface at the pinion being exposed to water, grime and not being rust proofed in any way!

When the V11 series arrived they'd had enough time to have a think about it and coupled with changed internal ratios in both gear and bevelbox the sealing mechanism and pinion bearings were redesigned and improved and a breather was added to the bevelbox that was also enlarged to take more oil and greater volume. One of the biggest problems with the V11 series breather set ups is actually on the gearbox where some genius in the design department put it in the centreline of the gearbox directly in line with the spray line from the rear tyre when it's wet! With no hugger or spray protection riding in rain can and does result in the gearbox filling up with water!

Later still the CARC bikes have another system where the pinion is sealed but because the entire bevel gear system sits within a reactive bridge with the bevelbox casing as well as the pinion being sealed there is another 'Rubber' boot that seals the front of the box ensuring the interior of the swingarm remains 'Dry'. The CARC bevelboxes have a breather at the front of the bevelbox case above the pinion bearing part of the reactive bridge. It too is prone to water intrusion from wheel spray but, inexplicably, not on all bikes! The only reason I can think of is different spray patterns from tyres with differing sipage! Anyway, a remote breather to replace the shitty little 'Top Hat' breather is commonplace on CARC bikes. I in fact designed and marketed a very neat and unobtrusive system for the CARC early on but, as you would expect from Guzzi owners, they whined and complained that it was 'Too Expensive' so nowadays most people just use a banjo and a length of braided hose run up the swingarm and up near the airbox to allow the box to vent without the risk of water intrusion.

Cali 14's, V85's and other Smallblocks all have sealed pinions and breathers.

To return briefly to the subject of Quotas, (And others with the early *Unsealed* pinion bearings.) the thing is that although in theory the box should be able to vent through the bearings into the swingarm reality is such that sometimes, for whatever reason, the box will pressurise and the seal/s pop. I've experienced it myself with weeping seals that when you push in the seal hook to extract them you get a hiss of escaping air! Far more than you would expect if the full volume of the swingarm etc was available for expansion.

Anyway the 'Why?' Is by the by but I'd think that the reason why the Quota in question has the breather fitted is because it's one of these *Inconvenient* pressure prone boxes. You could always remove it, get the box good and hot and then 'Burp' it and see if it has excess pressure. If it doesn't? Leave it be. If it hisses at you? Reinstall the breather post haste!

[Chuck]

Well, that should cover it. Thanks, Pete.

[Pressureangle]

Here's the thread on what I had to do with the Sport to get it dry. I originally simply vented the cap to a hose, but it was so bad that it still pushed juice out a 1/8" hose over 3 feet long. The trick was shielding the base of the vent from thrown oil, which took a while to suss out. Since this mod, I've had zero trace of oil in the vent hose, I even ran it for a day without the hose and it stayed dead dry. 
 

 

[docc]

10 hours ago, gstallons said:

Did you finally get your rear end to not leak ?

Um, yep . . .   

[MartyNZ]

20 hours ago, docc said:

Our V11 LeMans/Sports have an elegant breather vent on both the reardrive and the gearbox.

Why not add one to your Quota reardrive and loose the "artisan" solution?

 

I tried an idea on my V11 to both reduce any chance of water ingress and reduce unsprung weight. An alloy vent plug with an oil trap, and a short hose with a foam filter. No oil leaks or water, but then there wasn't any before I started either. 

   

[gstallons]

Unsprung weight savings , I'm all in !  What is all the goop on the drain plug ?