I tested Sparkybackup twice now, and in both occasions it creates the ISO just fine. I am not creating an EFI iso or anything like that, just a regular legacy iso of my system that comes out at 2.9GB. I have used remastersys in the past and never had this proble. I have written the created iso with the USB writer included with Sparky, with dd, and even tried on a windows machine with Win32 image writer. I am using a USB flash drive that works for booting if I write the standard Sparky distro so I know that works.
When I try to boot the USB backup it just does not work and I go right to my installed grub menu (on my HD). Any ideas WHY?
When it stops?
Can you try to boot the backup is in a virtual machine?