On winter mornings, or after I do not ride the bike for a week, I find it very hard to start my bike. Last night I left the covers of my bike so that I could make a quick get away this morning. It didn't happen, my bike would not start. I guess the morning cold got into my bike. I always put the choke on full and pump some petrol into the carby before I press the Start button. In summer, my bike is OK. In winter, I can hear my battery getting flatter and flatter with each attempt to start my bike. Is this a sign that my battery needs to be replaced? Or am I hopeless at starting my bike?