How do I remove the drive sprocket on my chainsaw?

Hi, I've got an electric chainsaw which I wish to re-wire as the mains power cable has a nick in it. I've disassembled the casing and the only thing that appears to be holding the 2 parts together is the drive sprocket. How do i remove this to gain access? I was hoping to remove any wood chippings etc that might be inside too.

Many thanks, JPC

JP Clarey
September 2010