Hey ubaZdradamanto
It might be helpful to identify what country you are located in.
The 2006 B650 was the Air/Oil cooled SACS engine...in Canada the 650 was not watercooled until 2007, and in 2006 the big bandit was also still a SACS engine, not a water cooled 1250 until 2007,
Either way, it is NOT likely that the exhaust can (muffler) is the same...often they can be made to fit, but on the SACS 600/650 the muffler was welded to the mid pipe, whereas on the 1200, it bolted on.