Final Drive high level breather

No matter what I do (except stay out the rain) the oil drained out of my FD is always polluted with water. I spoke to Mikeyboy who looked at the FD and he reckons the only realistic way it can be getting in is via the breather as water pollution in only rarely a problem on non-breather FDs. The location of the breather means it is constantly sprayed with water in rain and its very simple design (perhaps too simple) means it would appear to be very easy for water to get in.

Touratech do a replacement but it's £56!!! https://shop.touratech.co.uk/reloca...1200gs-adventure-2008-2013-and-from-2014.html

I had replaced the breather in the past in attempt to cure this problem so decided to try a home made solution using the old breather and a box of spare parts from various scotoilers (which definitely don't fit to big Gs's).

Here's what i did...
(crap photos)

The pics are all out of order when loaded up here but what we have is
Oil out the FD after 7,000 miles. The black oil around the edges is from the rocker covers, the milky coffee coloured stuff in the middle is what came out the FD.

The "new" and the old breather side by side the old one with its "skirt" up. You can see the simplicity. A rubber tube with a hole in (its big on this one as I had been experimenting) and a skirt that covers it up and rests against a lip to seal it. The seal seems very poor. Also the breather is a just a push fit so possibly not the best of seals.

The brass spigot I tried at first. I simply pushed this into a hole I punched into the top of the breather.

And a couple of shots of where the breather fits.

more pics and commentary in next post....

part 2

Part 2.....
I sealed up the proper hole in the breather with silicone sealant and sealed the skirt to the lip with the same. Left it an hour to cure. Applied some silicone grease to the mating surface and pushed the breather back into place on the FD. This wasn't as easy as I had found removing the existing one and silicone squidged everywhere. I just did the best I could. It looks like it should be OK.

I decided the brass spigot thing didn't make a good seal so replaced it with a bigger plastic one.

Onto the plastic spigot I pushed a short length of rubber tubing and then some vacuum tubing of enough length to reach up to the tank. At the top end I added a Scotoiler reservoir breather which has a small filter in it. I then silicone sealed the Spigot into the top of the breather.

Now all thats needed is to cable tie it all in place.

part 3 - finished

The nearly finished job. You can see the top scotoiler breather just poking out under the tank top cover. It shouldn't let any rain or washing water in from there. I have been for a ride and it all stayed in place and, as when I mocked it up you can blow and suck through it all I should allow the FD to breath OK. Proof of course in the pudding but that will have to wait for 6000 or so miles until I service it next, or until a seal blows somewhere.

I have the 2008 post facelift model with larger internal bearings and no breather. I use at least 200ml of oil and have never had a seal blow or had water ingress. It leaked only when the main wheel bearing and oil seal failed.

On that basis you could simply bung up the breather hole and be fine.

If the breather hole was threaded you could have made up a banjo fitting.

I put a high level breather on a Mk 2 final drive (2009). Made a banjo fitting to replace the filler plug but even with a small oil separation can I could not stop it blowing a small amount of oil out of the breather.
Ended up plugging the breather until the final drive was warm then neutralized the air pressure and replaced the plug.
Only mentioned this in case someone is thinking of wasting time trying to fit a breather to Mk 1 & Mk 2 final drives.
The MK 3 ( 2010 to 2012 with breather fitted and the outer support bearing in the oil bath) has a different internal design with larger internal cavity.
If I was going to encounter deep water I would fit a high level breather to the MK 3 final drive.

Mistacat said:

I put a high level breather on a Mk 2 final drive (2009). Made a banjo fitting to replace the filler plug but even with a small oil separation can I could not stop it blowing a small amount of oil out of the breather.
Ended up plugging the breather until the final drive was warm then neutralized the air pressure and replaced the plug.
Only mentioned this in case someone is thinking of wasting time trying to fit a breather to Mk 1 & Mk 2 final drives.
The MK 3 ( 2010 to 2012 with breather fitted and the outer support bearing in the oil bath) has a different internal design with larger internal cavity.
If I was going to encounter deep water I would fit a high level breather to the MK 3 final drive.

Click to expand...

Pity I didn't swap my Mk2 FD for a Mk3 when the original bearings came to end of life.

BTW where is the filler plug? I use the speedo sensor hole with a large syringe for oil measuring.

My LC FD has one of those. It fell out recently when I was greasing the fd splines. At least I now know what it is

Just a thought. The Yamaha Diversion 600 (aircooled basic UJM) has a breather hose problem that fills the air-box with oil. When a larger bore breather hose is fitted, the oil blow by stops happening.

Maybe the GS final drive will be less likely to blow oil out if it has a large(r) bore hose. The bore of brake hose might be too small to allow air to escape without pushing oil along the pipe.

On the 2009 FD the filler was just to the left of the speedo/abs sensor.
separate filler is not fitted on the 2010 ( Mk 3) FD so use the sensor hole.
Agree regarding the larger bore hose but I made a stainless steel expansion cylinder that was mounted vertically half way along the hose which should have had the same effect.
I put is down to the oil being so aerated that it was not getting chance to separate out. No longer a problem as mine is now a MK3 and so is my spare .

My 2010 mk3 with breather has a ? filler plug to the right and bellow the speedo sensor. Can't see how there will be much air moving in any direction from the final drive. I still put 240ml. in mine, which is just up the the fill hole I mentioned previously.������

Kenny Rodkiss said:

My 2010 mk3 with breather has a ? filler plug to the right and bellow the speedo sensor. Can't see how there will be much air moving in any direction from the final drive. I still put 240ml. in mine, which is just up the the fill hole I mentioned previously.������

Click to expand...

Stand corrected the Mk3 does have a filler / level plug as stated, I have just got used to filling with a measured syringe through the sensor hole.
I also agree that in theory the only air movement should be through expansion and contraction. ( very little). On a Mk2 final drive I had 1 meter of 5mm i/d hose with an oil separator in the middle exiting under the top box and it still discharged oil so had to plug it. I put it down to aerated oil being forced to the top of the FD housing by the crown wheel. The breather on the MK3 is better sited.

A circular casing with a turbine wheel inside has to be a recipe for very aerated and splashed about oil. This is why I don't use the paltry fill volume that BMW recommend. Bear in mind they used to state 220ml but reduced it to 180ml because of complaints about oil vent leaks. The FD only has to see out the warranty period so what do they care?

Next time I'll try 240ml.

I like to use the Mk1 oil drain method - undo the paralever and tilt the FD back to drain via the speedo sensor hole. This recirculates grease around the paralever trunnion needle rollers and allows the drive shaft splines to be greased.

Just to finish this off, my home made high level breather does indeed seem to work. I serviced the bike today and drained the FD oil - nice clean non-mayonaissey oil despite lots of wet miles since it went in plus many bike washes and jet washes. Hurrah. I think I will go back to an FD oil change every 12k now.

The oil as it came out today....

AustinW said:

The nearly finished job. You can see the top scotoiler breather just poking out under the tank top cover. It shouldn't let any rain or washing water in from there. I have been for a ride and it all stayed in place and, as when I mocked it up you can blow and suck through it all I should allow the FD to breath OK. Proof of course in the pudding but that will have to wait for 6000 or so miles until I service it next, or until a seal blows somewhere.

Click to expand...