Good points guys.
I personally would much rather stick to KTM's design specs and recommendations: 10w-50 full synth.... Preferably Motorex. Motul, Castrol, Bel-Ray, Maxima, and Repsol also make great full synth 10w-50's for motorcycles with JASO MA wet clutch certification, if you can't get your hands on Motorex.
However, if one has to run semi-syth or non-synth it is important to stick to the same weight. Changing low temp (first number) and high temp (second number) viscosity can adversely effect engine operation. The LC8 is designed for the mechanical resistance that the 10w-50 oil viscosity imparts on the engine parts.