The new Google Maps allows you to export as KML directly via My Maps, and appears to have been vastly improved since Maps Engine Lite first showed up.
- Click the Menu button
- Click 'My Maps'
- Click 'Create'
- Click the Draw a Line button then 'Add biking route' and start tracing your route*
- Click the three dots button to the right of the 'Add Layer' and 'Share' buttons, then 'Export to KML'
- Select the relevant map layer, choose between KML and KMZ**, and click 'Download'
* Note that you can only add 25 points along an A-B route, and you can only have 12 A-B routes per layer.
** If you export as KML it's easy to edit these files in Notepad++ or similar and join multiple A-B routes together for longer journeys. You can then re-import your edited KML into My Maps, Google Earth, or a GIS.