Unibiased reply...
  They only last 2 years at the most and need replacing frequently..
 
  On a serious note, Ive sold two to guys in the states who have had theres fail on early bikes (which obviously causes a lot of damage). Its not a problem I dont think - more a case of preventative maintenance..Im having one fitted next service/rebuild for what it cost me. 
 2 left now..cheers guys 
 Cheers
 Nat 
 [Edited on 13-10-2005 by Nattyboy]