My 1999 CBR 600 has started playing up! I can go our for a ride on it and it starts no problem - but say for instance - 1/2 hr later I want to call for petrol (or otherwise just turn the bike off) - when I caome to start it again it acts like its as flat as pancake - it's not the battery as the lights are fine - could it be the starter motor? I am just getting into motorcyle maintenance and would appreciate any help on the matter.