A very excellent product is Professional Audio Tape Head Cleaning Fluid from American Recorder Technologies, S-721H. It is non-alcohol and recommended for tape heads, guides, capstans and pinch rollers:
http://americanrecorder.com/catalog/product_info.php?cPath=12&products_id=108
Jon
http://americanrecorder.com/catalog/product_info.php?cPath=12&products_id=108
Jon