Backing up Time Machine to External Drive

HI

I have an IMAC which has 1Tb Internal HD.

I have a 2Tb external HD connected by USB2 partitioned 1.25Tb & 750Gb.

The 1.25Tb partition is running Time Machine but running out of space and deleting oldest copy.

I just bought a new 4Tb External usb2 drive partitioned to 1.4Tb and 2.6Tb.

I am in the middle of copying the Time Machine backup folder to the new drive (Partition 1.4) then i will reformat the old 2tb drive as 1 partition and move the backup time machine back and use that drive solely for Time Machine.

At the moment it is still got 18Hrs left to copy from nearly 24 (i think at start all it would say was a day) using finder. Is there any faster way of copying 1.2Tb of the Time Machine backup folder so i can move it back to the newly formatted (old drive) after formatting it>

By the way i cannot repartition the 2Tb drive with time machine on it to give it more space as disk utility will not let me do that..

Hope i have made it clear, if not let me know.

Keith