Last year I had a sticky exhaust flap on the GS where the symptoms were a squeak from the central pivot as it was seizing up and struggling to operate . This happened when the ignition switch was turned on, I was worried the flap would close shut - thus blocking exhaust while in Spain. BMW (Blade Motorrad of Bromsgrove) wanted near £300 for a new flap fitted with labour so I decided to have a go at freeing it up myself first.
I took the flap off by removing the silencer via the clamp bolt then unscrewed the other clamp bolt to remove the flap by slackening off the Bowden cables. I took care in noting the position (angle) of the flap unit relative to the cables so as to ensure I didn't re-assemble and put extra strain on the cables by not having them in the optimal location. Also noted which cable went where (front and back - or push and pull) before I unhooked them from the inner wheel.
Once removed, it was obviously 'stiff' and the butterfly valve required a good deal of force to close and then open. The valve is spring loaded and the spring was having no effect in opening the valve as it was too seized. The valve was seized in the open position so it may not have been an immediate problem - but better to try and fix I thought.
I used Mr Muscle to clean off most of the carbon, and then suspended the whole flap unit in a bowl of petrol overnight. Afterwards I was then able to close easily, and it only required a slight bit of pressure applied to 'flip' the flap open again.
I then re-fitted using the following instructions (click on the image to zoom to original size):
If the above doesn't work there is a 'blanking' tube available from Nippy Normans here. This is intended to in-fill the space the flap takes up. The flap is only required for noise control at lower revs. As I understand the additional noise is negligible. Instructions come with the tube explaining how to remove the associated solenoid unit too (the bit that drives the cables).
