[NTLUG:Discuss] dd and cloning flash drive

[david]

Long ago i used unetbootin to create a bootable
flash drive with different tools.
I have outgrown that drive so i did:

/dd if=/dev/sda of=image.dd/

unplug old drive, plug in new one:

/dd if=image.dd of=/dev/sda

/Of course it didn't boot, even though gparted said
the boot flag was set. So i pulled the mbrs:

/file 2mbr.bin
2mbr.bin: x86 boot sector; GRand Unified Bootloader, stage1 version 0x3, 
stage2 address 0x2000, stage2 segment 0x200; partition 1: ID=0xe, 
active, starthead 32, startsector 2048, 7888896 sectors, code offset 0x4

file 4mbr.bin
4mbr.bin: x86 boot sector; partition 1: ID=0xe, active, starthead 1, 
startsector 8064, 3958912 sectors, code offset 0x31
/
4mbr boots, 2mbr does not. Why are they different?
What am i missing?
Thanks.