To update the title on your site you need to make a couple of changes in the Control Panel (CP)
1. Under 'Master Settings' choose 'Edit Site Descriptions'
2. In the field 'RSS Site Title' --> Enter your site title here
3. Under 'Master Settings' choose 'Edit Public Portal' --> Click Apply Changes to Public Portal Page
Although you have not made any changes to public portal this re-draws and calls the design changes that you made earlier to be pushed through the site.
Refresh the main page on your site to see the title has changed.