just think that also the both upper numbers are there for a good reason.
XCF obviously the model name, maybe 16 was a number for the variant
and Bi or maybe Bj could stand for the date? Bj is very often used in German speaking countries for "Baujahr" = model year.
That would be than hint to September 2002?
Sure the SID fork than doesn't fit date-wise well any longer.
@Obi-Juan you've said earlier it was used from a racing team. Any success googling for pictures of this racing team or form the pro racers of that team? Typcially there are still rankings or lists of leader boards from some earlier races available.
Just to help dating the period this racing team was existing and also using Kästle bikes...