How hard is to change ztl1 to ztl2? is it bolt on with no mods?
Yep. You just need the caliper, brake line and master cylinder.
For Buell XB you need :
H1110.1AMZT Caliper
H0507.1AMD Master Cylinder
Buell OEM Stainless Steel Brake Line : H1531.4AK for XB12X or H1531.1AMA for XB12XT (not sure abou this one) or H1531.8AE for others XB