Gearbox Breathers, who's got one

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When doing my gearbox rebuilds I always put a breather pipe in. Am I just wastin' my sorry ass time or does it make a difference .
Gearbox Breathers, who's got one


Worth it, or waste of time!

J
 
No breather needed -unless you seal the hole where the clutch cable goes in. [which isn't a bad idea if it rains where you live.] Jim
 
Don't the inspection cap covers all have a factory drilled little hole to let any air pressure out, seems all mine did/do?
 
1up3down said:
Don't the inspection cap covers all have a factory drilled little hole to let any air pressure out, seems all mine did/do?

Up until the MK3 they did, It lets the air out and the water in. I seal them all with a dob of epoxy. Jim
 
comnoz said:
1up3down said:
Don't the inspection cap covers all have a factory drilled little hole to let any air pressure out, seems all mine did/do?

Up until the MK3 they did, It lets the air out and the water in. I seal them all with a dob of epoxy. Jim

Gentlemen don't ride in the rain :)
 
illf8ed said:
comnoz said:
1up3down said:
Don't the inspection cap covers all have a factory drilled little hole to let any air pressure out, seems all mine did/do?

Up until the MK3 they did, It lets the air out and the water in. I seal them all with a dob of epoxy. Jim

Gentlemen don't ride in the rain :)

And what is your point? 8)
 
Yep mine is sealed and when I installed my dearly loved hydraulic clutch. I put a grommet over the pipe going into the cover, just under the hex head so it is sandwiched between it and the cover to keep moisture out too.. Some day I may machine the cover to take a real seal or O ring.
 
I had a problem with a gearbox made up of spare parts that had neither a breather or hole in the inspection plate. It performed ok for a while with a screw missing from the inspection plate, but once a replacement was found and refitted it pumped all its oil into the primary when hot. Took a while to realise it had a mk3 inspection cap and drilling a small hole fixed the issue!
 
Gentlemen don't ride in the rain :)

and "Gentlemen Do Not Motor About After Dark"

Joe Lucas's presumed response when asked why his headlights were so unreliable
 
needing said:
There is minimal risk of water entering the gearbox via the tiny inspection cap hole due to the angle of the cap when fitted (unless you wash your bike with a high pressure hose).
A greater risk is the more vertical clutch cable entrance which is easily overcome by putting a spark plug rubber cap on the cable and sealing it to the gearbox.

From a warm climate perspective, if the gearbox is hermetically sealed there is no room for oil or gas expansion as it heats up in use so it will find it way past gaskets or seals or more especially along the pushrod shaft into the clutchplates. If the pushrod shaft is also sealed then the weakest gasket and seal take the pressure brunt.

Even a garden hose or a rain with a bit or wind will put a few drops of water in there. That is all you need to cause the rust that is commonly seen on the shift levers and springs. Auldblue's fitting with a piece of hose pointing down is a much better idea. Jim
 
The MK3s, at least mine did, came with a small vent fitting near the top. Similar to what oldblue shows.
Jaydee
 
jaydee75 said:
The MK3s, at least mine did, came with a small vent fitting near the top. Similar to what oldblue shows.
Jaydee

Yes, and they should have a few inches of hose on it, down the back of the transmission. Jim
 
jaydee75 said:
The MK3s, at least mine did, came with a small vent fitting near the top. Similar to what oldblue shows.
Jaydee

My Dec 73 850 has that also (but no hose, I will fit one (now)

The 71 with no tube type vent had corrosion on the usual plate and dome head bolts.

Auldblue, if you put the vent at the bottom the rain won't get in.
 
Time Warp said:
Auldblue, if you put the vent at the bottom the rain won't get in.

Tried that time warp, the back end was all over the place and I couldn't keep it going in EP90!
 
All gearboxes and diffs have breathers, and always should. My 850 has a breather fitted just like the one shown except it is screwed in. Probably a good idea to fit a hose to it so long as the end of the hose cant suck in water [ I haven't yet had to and that bike has been ridden through some of the worse rain storms you could imagine ]. point the end of the hose down some where.
Dereck
 
needing said:
Hi all.
Please note the use of words like Major or Minor / Minimal.

If water does get in from riding in the rain or wetting the bike with a garden hose it should sit 'under' the oil i.e. oil still floats on water.

Just a thought: in a number of bikes I have observed, the standard cap vent hole may tend to plug with polish residue which resolves the ingress problem but will 'blow' out should the internal pressure rise sufficiently due to heat. :idea: :)

Gearbox Breathers, who's got one

It sits in the bottom until the oil gets hot enough to evaporate it. Then it condenses on the linkage under the cover and makes rust. Common on many Commandos. Jim
 
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