Final drive speed sensor oil leak....

[G5RJO]

Having fitted a new ( to me) final drive unit, I'm getting an oil leak from the speed sensor. Fitted a new O ring of the correct size, but after 100 miles I've got a slight weep again.

Looking on the parts diagrams, it seems that there used to be a washer specified as well as the O ring, I don't recall there ever being a washer on my 08 GSA; am I missing something here?

Also, the O ring appears to be seating just inside the sensor hole, should it be at the bottom of the hole?

Roger.

 

[Mistacat]

I have only seen them with a green "o" ring and a washer on 08 & 09 bikes.

 

[NicD]

photos?

 

[UturnTony]

Every sensor i have removed on bikes of different years there has been a metal shim type washer that goes up against the sensor body.

The O-rings i have seen have all been green; if you have fitted the sensor correctly the body will be sitting flush with the FD and the O-ring will be in the correct position inside the sensor bore.
If the sensor does not seem to, with a firm push, go in and immediately sit and stay flushed up against the FD (it should not need to be "pulled in" with the bolt) then the O-ring may be the wrong size, is trapping, and not sealing properly.

The above is an attempt to address the op's query based on my experiences over the years and is not meant to be authoritative

 

[oddshapedballs]

Only ever seen a green o-ring on SC's and TC's.

 

[G5RJO]

Thanks everyone, I have changed the oil in the FD on many occasions and never seen a metal shim, the parts fiche shows a shim but it was greyed out as if no longer utilised. I have a few new 15 x 2 'O' rings, so that's correct, I've ordered a shim or centering ring as they call it from BMW for the princely sum of £1.50, so I hope that solves the issue...

Roger.