I know this question is old but it is still valid. I was never able to write a Mac installer image to my Flash Drive and have it bootable, unless I did it on a Mac. Using Micheal D. M. Dryden's Link, I was able to use the Diskpart command to clean and prep a GPT partition on a flash drive for an OSX Mavericks install image.
I used TransMac on Windows 7 to restore the image file I had to the Flash Drive, it created a bootable Mac image on my flash drive. Someone had reported that the method for using DISKPART did not work, but I have done this twice and it works remarkably well, and it's the only method I could find to create a Mac-Bootable Flash. I've been trying to post this to confirm that it works for some time, I just hope it helps someone else, because it is a very easy solution.
Here are the Diskpart commands used to prep the Flash Drive, just to have them here in case my Link does not work:
diskpart
DISKPART> list disk
(Find the disk number)
DISKPART> select disk x (from result of List Disk)
Disk x is now the selected disk.
DISKPART> clean
DiskPart succeeded in cleaning the disk.
DISKPART> convert gpt
DiskPart successfully converted the selected disk to GPT format.
DISKPART> create partition primary