Since I'm still waiting for someone to buy one of my motorcycles and thereby
 provide the cash required for my rebuilt engine, I'm puttering around with
 all the old parts and trying to sleuth out the cause of the failure in the
 meantime. Press "delete" now to avoid boredom.

 If someone has a fiche for the type IV <Joel?> or a parts book, maybe you 
 could help here: The part # of the cam bearing that _didn't_ disentigrate
 is 021 101 521. The part numbers of the bearings that _did_ fall apart
 are 113 101 511 and 113 101 522. Since most type IV parts have an 021 
 prefix and the 113 prefix is generally found on type I <upright fan> engines,
 I have become suspicious that the bearings may have failed simply because
 they are the wrong parts. "How to Rebuild Your Air-cooled VW Engine" states
 that the type I and IV parts look the same but are NOT interchangeable. 

 I'd like to understand this failure so that I can prevent the same thing
 from happening in the future. It's a real heartbreak to dis-assemble an
 engine which clearly had a lot of life left in it <the cross-hatch hone marks
 are still visible on the cylinder walls> to find a problem caused by what
 may have been poor attention to details <looks right, who cares about the
 part number>.

 Thanks,

 Dave