A reverse caster suspension apparatus includes a tiltable platform assembly that is interposed between a sprung axle assembly and a vehicle structure. This arrangement provides an efficient means for changing the caster angle without harmful distortion of springs, and without requiring complex special-purpose suspension design and components that would likely be subjected to excessive wear. The platform assembly includes a platform frame to be connected to the vehicle, a nested, pivotally connected suspension frame to which the axle assembly is attached, and an actuator mechanism coupled at high mechanical advantage between the pivotally connected frames. A pivot axis of the platform assembly can be located approximately in line above respective spindle axes of the axle assembly for facilitating operation of the actuator at low power, and the actuator preferably holds its positive-caster condition with no applied power.

A rotary valve head system for a multi-cylinder engine includes hollow intake and exhaust rotary valve tubes having multiple apertures registerable with an engine intake or exhaust manifold according to a timing mechanism linked to the rotary valve tube. A cylinder head overlying the multiple cylinders includes head intake and exhaust ports registered with the cylinder intake and exhaust ports, which is configured such that a clearance is provided between the cylinder head and outer surfaces of the intake and exhaust rotary valve tubes. Inserts are positioned within the cylinder head to form a seal between the intake and exhaust rotary valve tube apertures and the cylinder head. Incoming air/fuel is permitted to flow through the intake rotary valve tube until entering into a cylinder through a tube aperture registered with a head intake port and cylinder intake port. Outgoing combustion products likewise flow through the exhaust tube.