Suzuki AN125 Scooter starting problem?

My 14 yr old Suzuki AN125 scooter has done 10k miles. Whilst it is a good workhorse, it has always been a problem to start. The self starter fails to work unless the battery is fully charged. However the battery does not seem to keep its charge, even if used daily. The kick start sometimes starts after a couple of goes, but can take a dozen kick starts to get going. Any suggestions what is causing this problem?