[dyzio]

That's on the Prilia, isn't it?

Try taking the rear seat plastics off, you'll see the reg/rec, starter solenoid. Check of dodgy connections.

Is that 13.5V on a separate volt meter or the built in one?

You can easily improve it, do the wire mod, it's a sticky on AF1.

Did you know the previous owner? If he use the bike occasionally and didn't use an optimate, the battery might be on it's way out. I had that, one day it just refused to do anything.