The above analysis assumes a point mass (i.e. with all the mass concentrated in a single point located at the centre of mass and all the forces acting on that point).
However for a motorcycle on the wall of death, although the weight acts through the centre of mass, the friction acts at the wheels (on the wall).
These three forces (friction forces on each of the tyres, a weight force through the centre of mass) balance but are not in the same line. Which means the motorcycle will tend to rotate and tip over.
The normal reactions from the wall (acting where the tyres touch the wall) cannot help to balance this torque because they will not produce any turning effect if the motorcycle is perpendicular to the wall: