Gearbox Breathers, who's got one

dynodave said:

.. Seems to have been a waste of time ?

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And would you be surprised ? .

One could drunk tranny in water and see where the bubbles come out for sense of how ventalated it is from the factory or just tip in various directs to see where oil leaks out and how much with warmed oil or better ATF. Even just parked long term condensation will collect inside above oil level so why worry with venting when just paint or grease or SS parts above oil solves rusting. On long trips I've found its not so much the high loads on tranny so much as just combustion heat having time to equalize. I've not heard of mayonaise seen in Norton gear boxes so far. One vent area no one thinks about but me d/t Peel revealations - is the open to air unsealed end of DS sleeve bush. To get idea of how much friction heat vs conduction heating in gearbox is to feel final drive chain temp after some intervals of various loads.

My TTI tranny appears very sealed up, no hole in fill cap, only the entry of cable hole, so should it be vented any more?

Ta.

If there is any water layer at all on the bottom operation will about immediately make mayoniase. Unless an over head water leak into tranny or too slow deep water crossing above it then only water inside will be whats condensed above oil level though enough of it can drip down to bottom. There's always some moisture dispersed in lubes not held over boiling a fair time but not hardly ever collecting a layer on bottom. There's a bit of sliding scale of equilibrium absorbing vs evaporating with temperature so merely warm a decent time does shift this to less moisture.

Torontonian said:

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. :|

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hOW HOT DOES THE WATER IN THE OCEAN HAVE TO GET, FOR WATER TO EVAPORATE OF THE SURFACE? I don't know the science behind this.

I also wonder how hot Hobots G/box gets after he has done a hard run???

Its a sliding equilibrium, water absorbed vs water evaporated both going on at once so as long as above freezing and ambient air dryer than the oil the oil will tend to dry out but even boiling oil for a long time will not drive all the water out but nil left to matter. Cold fluids then to hold more gases than hotter so extra temp shifts water vapor out of oil. Oil won't hold much % water so don't store items in oil bath if not supported off bottoms and bottom better be rust proof or hermetic sealed with dryer agent inside and oxygen expelled and no electric battery action of touching items. On this subject I once used wd40 to protect stuff a few days till sealed to find over night condensation had floated dam wd40 off surface to see many islands of rust merging like fungus so wd40 is now only a mild cleaner to me that smells bad.

Apparently Norton started using the brass gearbox breather screwed into the inner cover on the 850 Mark II and IIA's. That is according to the Mark II/IIA parts supplement. What I found interesting though is that the same parts book lists both the vented and the non-vented inspection covers. This appears to be one of the many mistakes in the parts book supplement. However, I have an old service manual published by Clymer publications that shows a brand new 850 Mark II engine number 311998 that was dismantled and reassembled for the photo shoot. Looking at the various pictures of this bike it shows that it did indeed have both the brass vent and the vented inspection cover! Just think, that bike had twice the chance of getting water splashed into the tranny as one with just one vent! So if you have an 850 Mark II/IIA it might be worth checking to see if your gearbox is also vented both ways.

I found that the brass vent on my gearbox to be a little too short for putting on a breather hose. So I made a longer replacement vent from a piece of 3/16" diameter brass stock which is a pretty straightforward part to make.

Cheers to all who answered, recon I won't bother with breather on this box although Mick H does say if your cap doesn't have a hole fit one, dynodave says his experiment proves there is no need and that it was a waste of time posting his initial post, but he still can't stop Goldielocks from eating his porridge in the mornings.
Jim Comstock also recons total waste of time.

J

My Norton sat under a tarp for many years. When I resurrected her the Norton's gearbox was overfilled . . . . . Hmmmm? Turned out the bottom of the box was full of water, not so high as to ruin the gears or shafts but high enough to force a prudent change of bearings.

Someone said, the water must have got in by way of condensation running down the clutch cable.

auldblue said:

Jim Comstock also recons total waste of time.

J

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I wouldn't say that -or at least I didn't mean it that way.

I would say it is a waste of time unless you seal the clutch cable entrance and the original breather hole in the cover.

As far as I am concerned all Nortons should have the clutch cable entrance sealed and the original breather plugged. Then you should install another breather with a hose pointing down. Jim

Uh, still leaves the dry above oil level splash reach venting in/out the outside sleeve bush that AMC knew didn't need an oil seal not to weep, unless lain over too long after crashes which is a good thing for sleeves bushes. For the moisture plagued owners most other wise well sealed gear boxes have filters with desicants for some extended corroison prevention. Jim maybe ya could put a thermometer on the cradle and gearbox to see which way heat flows.