I wanted to post these links.... Lots of good info... http://www.etuners.gr/psamini-1-6-thp-timing-problems-camshafts/ http://www.etuners.gr/peugeot-citroen-thp-engine-maintenance-servicing-101/
Yep good info there. Etuners even went so far on a build as to key the crank where the lower timing sprocket sits. Definitely a permanent solution. Still boggles my mind that friction is the only thing holding that sprocket in place. Not sure what BMW was thinking by letting that slide through engineering.
Well... They aren't the only ones that do that kind of stuff... Just last week a fellow stopped in with a 5th gear out of a manual transmission. The gear was a 2 piece friction fit assembly out of a Datsun 2000. Made a slight mod so the two pieces act as one.... Fixed...