thanks guys
the problem in my bike could have resulted from all 3 reasons, as my skid plate was bent, the rubber inserts were torn, and one of the engine screws (the one hooking to the connector above the carb) was loose
since the crack is only partial and only on the left case i will take it tomorrow to someone that specialize in magnesium welding, and if this wont work i'll order the cases (i see that 2012 has same partnumber - so i'll go for 2013).
i also saw a post where someone switched internals of 2008 with 2011 (280), so i guess that differences were minor over the years
thanks