[Iorek]

OK, trovato. Da un documento ufficiale del 2002 di BMW North america (si trova in rete, se vuoi te lo linko in MP):

"Recent tests with the F 650 CS(A) have proven that the mileage
interval between drive belt replacements can be greatly
increased.
The interval between drive belt replacements has been doubled
from the original 12,500 miles to 25,000 miles.
The drive belt should be checked for damage as part of every
check up, service or inspection, and replaced as necessary. The
following descriptions should aid in evaluating damage as relates
to drive belt replacement."