POSTED in the DRZ forum, reprinted here.

DRZ and RMZ are completely different motorcycles.

there are/was 4 models of DRZ. S (dual sport),E (off road electric start),K or kicker (off road kick start only) and SM (17" street wheels, upside down forks,etc).

S was introduced in 2000 and still available for 09.
E was introduced in 2000 and was discontinued in the US for 08.
K was introduced in 2000 and was discontinued in the US for 04.
SM was introduced in 20005 and is still available for 09.

S,SM,04 and newer California model E and 07 E have the same cams, compression and carb.

00-06 49 state E and 00-03 K have the better cams,FCR carb and more compression.

To confuse you more, Kawasaki and Suzuki did an alliance in 03. the 2003 KLX400r and KLX 400sr are just green DRZ’s. R is a E model and SR is a S model.

These are the US models.
Different country of import have other differences, pair valve, gear position ignition restriction, ect ect