The bottom fixing 'lugs' on mine broke
(see www.sibirskyextreme.com/2009/08/page/2/ about a third way down)
The Haynes book and BMW stickers on the unit said nothing was serviceable.
Those wonderful chaps in Komsomolovsk (and their mates in the military aircraft engineering workshops) built a new part from steel and fitted it. It then got me through the toughest ride of my life - and then 5,000 miles home.