Gearbox Breathers, who's got one

Don't much see how gearbox temps. could ever get hot enough to evaporate water and in there is the problem of outer gearbox retaining moisture for rustage . But yes it happens , no issue with inner gearbox. Moisture collects so a little airflow probably an idea after contamination , or as above thoughts preventing water entry in the first place. Reach down and touch the gearbox cover at a stoplight and see how cool it is. :|

Seems to me that if one were to plug the vent hole in the inspection cover, and seal the well where the outer sheath of the clutch cable sits in the adjuster nut, the GB will adequately vent thru the annular space between the inner clutch cable and the outer sheath, even if the cable is lubed or oiled.

Slick

Yup , makes sense ,so you really don't much need a GB inspection cover with a tiny breather hole to let in even more moisture to rust out the springs (which weakens them ). Sealed n' soilid .

texasSlick said:

Seems to me that if one were to plug the vent hole in the inspection cover, and seal the well where the outer sheath of the clutch cable sits in the adjuster nut, the GB will adequately vent thru the annular space between the inner clutch cable and the outer sheath, even if the cable is lubed or oiled.

Slick

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It probably would. But you want to avoid any positive pressure in the gearbox as pressure will help move the lube down the mainshaft toward the clutch.

Needing, Maybe you don't ride your bike long enough to get the gearbox up to temp but I will guarantee that after a day ride across Tx in the summer my gearbox is warm enough to evaporate the moisture.
And if you haven't seen the accumulation of rust in a gearbox cover then you haven't worked on many Commandos. Jim

Yoose guys don't seem to understand what it took on Peel to more than match pissed off sports contesters I boldly brag about so can assure you after a gallon or 3 spent in 15 - 45 minutes in lower gears WOT or up-downshifting like crazy Peel's AMC was too hot to handle especially with good heat carrying ATF. I don't know if world class Norton racers get their trannys as hot as Peel did a bunch of times as their heats are over in a few laps so one good go almost 90 miles a leg in Mt twistes in little over an hour likely covered as much as seasons of race events.
Even so moisture evidence showed up in Peel so changed fluid about once a season pissed seeing bushes gold dust.

There is too much breathing holes in AMC, to point mere mild warmed use and cool down plus weather fronts will condense micro layer after micro layer on till items above oil level rust up. There is no blow by so inhale/exhales happen over minutes or hours and nothing inside to vaporize but maybe mild moisture so nil pressure can ever develop unless ya really do try to seal up and then rather low to contain but likely impossible d/t the leaking shafts. Just grease or paint the vulnerable stuff and forgetaboutit till next time in. What can matter is a fairly soon new rebuild lube flush and change.

If you get lucky you might get both prizes, a few rusty selector parts and that other chestnut. :lol:
It annoyed me long enough so one day the cover took a spin.

Ta.

needing said:

comnoz said:

Needing, Maybe you don't ride your bike long enough to get the gearbox up to temp but I will guarantee that after a day ride across Tx in the summer my gearbox is warm enough to evaporate the moisture.
And if you haven't seen the accumulation of rust in a gearbox cover then you haven't worked on many Commandos. Jim

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Incorrect on first sentence. Texas and South Australia appear to have similar temperature profiles. Distances = 150+ km is common and still no rusty sauna in my gearbox.

Correct for second sentence: I offer my experience of my bike with my enhancements. How we all may choose to allow/disallow water ingress and associated rust is what this forum is about.

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Agree 100%

But Texas is 800 miles long and 600 miles wide. Jim

Driveable Canada is 3500 miles wide and 500 tall . Cool most of it. :|

One can't ignore the simple time factor of combustion heat conduction via the cradle as much or more than internal friction. I've stopped in intervals feeling the head flows and alloy cradle speed up heat creep to tranny. At one time I thought scine England had such moist cool climate that they'd solved moisture problems so nothing much to be concerned with till had a look in. The infamous pawl spring is a common victim of living above lube level and possible the small steel fasteneers swell up trapped to twist about flush. I perfer clear wheel paint as over spray unnoticed and grease is messy to handle but so little = 0ero oil ever gets there [w/o crashing] it remains in place.

Ta.

The sun has risen and the sun has set and we ain't out of Texas yet. Rode 12 hours from Houston to Van Horn, Texas. Nearly ran out of fuel a number of times. Moved onto the shoulder and throttled down. You can smell and or feel the heat coming from a town before you get there. Slept like a baby that night in Van Horn. Two more days to Los Angeles. Young and full of it.

.

needing said:

Ho! Ho! Ho! The gearbox oil is hot enough to "evaporate" water!

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Erm, why not? Even soldified water - commonly referred to as "ice" - evaporates. Temperature just drives the vapour pressure differential and thus the evaporation rate.

Tim

No-one thinks water in the bottom of the gearbox is a good thing (speak up if you do), but atmospheric moisture condenses out of the air above the oil level and in the outer cover and wets the steel surfaces which are not in oil when the metal is cold.

That water rusts those steel surfaces and some of the water even ends up in the bottom of the gearbox!

Anyone tried lightly pressurising their gearbox, to see how many de facto "breathers" it has?

Dynodave did a thread on it 2012 says plenty . But Mick Hemmings is shown on a gearbox rebuild pictorial fitting a breather.

J

I would think that a breather cuts both ways: It keeps GB pressure near atmospheric while running, but, as the GB cools, it draws moist air in while static. If the GB breathed through a charcoal canister that received engine heat it would exhale while heating up and draw moisture free air while static; problem solved??

GB oil is relatively inexpensive and easy to install.

B.

Tintin said:

needing said:

Ho! Ho! Ho! The gearbox oil is hot enough to "evaporate" water!

Click to expand...

Erm, why not? Even soldified water - commonly referred to as "ice" - evaporates. Temperature just drives the vapour pressure differential and thus the evaporation rate.

Tim

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Sublimation is the transition of a substance directly from the solid to the gas phase without passing through an intermediate liquid phase.

Needing, water doesnt have to get to 100c to evaporate. Heck, it evaporates at room temperature. The vapor pressure of water goes up as the temperature rises and it leaves its liquid state at a faster rate.
I've seen rust on the bolt heads or hairpin of every box I opened.
Jaydee

Triton Thrasher said:

No-one thinks water in the bottom of the gearbox is a good thing (speak up if you do), but atmospheric moisture condenses out of the air above the oil level and in the outer cover and wets the steel surfaces which are not in oil when the metal is cold.

That water rusts those steel surfaces and some of the water even ends up in the bottom of the gearbox!

Anyone tried lightly pressurising their gearbox, to see how many de facto "breathers" it has?

Click to expand...

Through internet magic you can restore the past, which people forget just as fast:
850-inner-outer-gearbox-leak-question-t12848.html#p151466

auldblue said:

Dynodave did a thread on it 2012 says plenty . But Mick Hemmings is shown on a gearbox rebuild pictorial fitting a breather.

J

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Well good on ya...I remember the experiment real well and the write up. Even I forgot I had posted it here. Seems to have been a waste of time ?