Mavericks Disc Image
In order to reset your Mac to your shipped OS you just need to boot it from Recovery Mode, but install from the Internet. It's probably installing Yosemite because you might be restoring from a backup or your possibly doing a Recovery from the drive (which in this case would be the current OS recovery: i.e., Yosemite)

Here is the difference between the two:


If you use the Recovery System stored on your startup drive to reinstall OS X, it installs the most recent version of OS X previously installed on this computer.
If you use Internet Recovery to reinstall OS X, it installs the version of OS X that originally came with your computer. After installation is finished, use the Mac App Store to install related updates or later versions of OS X that you have previously purchased.


See the how-to-guide and additional information reguarding Recovery HERE

NOTE it states in the docs that it automatically detects when the Recovery System on the startup drive isn't available, however you can manually elect this in the Recovery menu