That Motorsex stuff makes great lube I hear, but who has sex with their motor? Damn kinky Swiss, that's who!
edit - The reason KTM recommends Motorsex oil is because they don't make KTM brand oil and Motorsex has an orange cap.
As for the "W40" or "W50" in the XXW40 or XXW50 oils, Yamaha recommends oil weights for the FJR engine per the below scientific ambient temperature / viscosity chart:
You can clearly see that the first number affects only the cold end of the temp range, while the 2nd number affect how hot the ambient can be. Unless you plan on starting your bike at below freezing temps then 10W oils are not needed. 15W or 20W will suffice. The advantage of a W50 oil over a W40 oil is only 10 degrees ambient. But I call BS since this is a liquid cooled engine it will run at the same internal temperature regardless of the outside ambient.
So there you go. It doesn't really matter.