Final drive small leak R1200GS '14

[Alba]

Just back from a weekend away with some biking friends, doing some spirited riding and some off roading.  When I got home I seen some dark spots on the rear wheel only on the drive shaft side of the wheel.  On further investigation the 'black cap' had a thin covering of oil and only one of the cap screws, the back right next to the drain plug.

 

I use the bike daily for work, do you think it's safe to continue using?

 

Any advice on what my next steps should be to investigate the issue?

[Boxflyer]

Hi Alba,

It's safe to ride until you start to get an oil film on the rear rotor...which can be cleaned off with brake cleaner and still not ruin the pads.

This is pretty common, and I'd approach it with a couple of steps cleaning things before doing the final solution of replacing the Small Bearing Seal.

 

Firstly, with a narrow blade straight screwdriver, gently pry off the black plastic ring to expose the 2 part seal on the main axle shaft in the Final Drive.

The seal has a whiteish looking felt area designed to absorb some of the normal weeping from the seal since it is in constant contact with the Final Drive fluid.

The actual seal lip is on the inner part of the seal that rubs against the axle.  It doesn't take much dirt/crap/whatever to bridge that seal and allow what you see on your FD...that's maybe 1/2 teaspoon of oil loss all together on your bike, it just looks bad, and you have not compromised the quantity of FD lube at all.

Below are the first tools I use to clean between the seal lip and the axle.  

I was leading a group of 13 riders down from Anchorage to Portland back in 2014 and used the Marriott door hanger cut into the shape you see here to clean the offending debris on no less than 3 of the BMW bikes leaking FD's much worse than yours.

The Seal Mate is really the "cats meow" when it comes to cleaning seals like this.

This is the link to the "new IMPROVED" version on Amazon.

Seal Mate Plus

 

If after cleaning the seal and you still have leaking, you might need to replace the seal.

 

I use a small drill (maybe 3/32") to drill 3 evenly spaced holes thru the white felt part of the seal as you see below.  You want to aim for the outer edge of the white felt so you drill thru the gap you can see on the top seal in the picture below.

Just barely drill thru the steel frame of the seal itself so that the deck screws can get a bite on the steel body of the seal.

The deck screws have been ground down on the tips so that they don't drive into the bearing behind, but as they go thru the steel body of the seal, they start to evenly pull the seal out of the FD housing on the threads.

 

To replace the seal, just clean up any small shavings from the drill, and other road crap that may be behind the old seal and tap in the new seal...sometimes you need to use a blunt tipped instrument to get the outer metal ring to seat tight against the FD.

As you can see in the picture, I keep several of these on hand for any bike I work on that might need one.

Final Drive Shaft Seal MAX BMW

 

Hope this helps!

 

[Alba]

@Boxflyer this is really informative, many thanks.  The drilling and use of deck screws makes perfect sensor just feels like BMW has not thought about this replacement.

[Alba]

I found this YT and it looks like the process you describe.

 

 

[Boxflyer]

Yes, that’s the seal replacement procedure, but give a cleaning of the seal lip a chance…if it doesn’t work, you now see the easy next step. 

[Alba]

@Boxflyer this worked a treat. Getting off the black cap was not straightforward and there was a good quantity gunk.  Gave it a good clean along with the sahaft and used a set of feelers to get underneath the seal and got out some more gunk out.  Cap back on and it moves so freely, hour run into work today and no sign of oil.  Hour run home and no sign of oil  Thanks for the guidance.

[Boxflyer]

Glad that worked… you may still need a seal replacement in the future, but this way you can choose when it’s convenient. 

[MichiganBob]

Thanks Boxflyer, good information to file away for a "just in case."