This is mostly a reminder on how to do it, but maybe other people might find it useful.
I had a problem after changing my default Google Calendar (this was another adventure) my calendar in Evolution kept failing sync with timeout.
Tried to simply right-click and delete, but it would again fail with timeout.
So, first backup (just to be sure), and shut evolution down.
Then I went into the $HOME/.local/share/evolution/calendar/system and deleted all entries on that directory.
Then launched gconf-editor and under apps->evolution->calendar there is an entry named sources.
Double click will take you to the another window where you can find which of the xml entries is the one from Google (usually it is the last one).
Delete all tag relating to your calendars. In the end should look like this:
<group uid=”xxxxxxxxxx.xxxx.x@machine-name” name=”Google” base_uri=”google://” readonly=”no”></group>
Then just relaunched evolution. Everything is default now. Just reconfigure the Google Calendars and re-sync.