hi my son has the cbr 600 1998. does,nt get to use it much at the moment being in the uk, dry days only(there,s a laugh) anyway rode it to work no problem, came to start it after work, dead. he called me i said bump start it. it started, got about 8 miles it died again. trailered it home. the battery was flat. i charged it up and it started again, i checked the regulater input it was reading about 14 volts. am i right to suspect a faulty battery