If you don't want to modify BW transformations , there is another option in BPC.
You can implement UJD_ROUTINE to write a start routine. Data from BW will be captured through the implemenation of this BADI IR_DATA and you can cleanse the data, i.e remove line feed, carriage feed etc., using abap statements before importing to BPC . Please check with the ABAP guy.
Call this start routine in the transformation file in the options sections :
OPTIONS:
STARTROUTINE=<BADIFilter name>
Pl. try this option