Breather assembly for an internal combustion engine

A motorcycle engine comprising:

• a crankcase;
• a first cylinder assembly extending from the crankcase in a first direction;
• a second cylinder assembly extending from the crankcase in a second direction;
• first and second substantially identical rocker bases, each rocker base coupled to a respective one of the cylinder assemblies and defining a first breather passage and a second breather passage;
• a first breather assembly coupled to the first rocker base and communicating with the first cylinder assembly through the first breather passage of the first rocker base;
• a second breather assembly coupled to the second rocker base and communicating with the second cylinder assembly through the second breather passage of the second rocker base, wherein the second breather passage of the first rocker base and the first breather passage of the second rocker base are obstructed.

A rocker base for a motorcycle engine, the engine including a crankcase and at least first and second cylinder assemblies, the rocker base comprising:

• a lower wall at least partially defining a rocker chamber in communication with the crankcase;
• a plurality of rocker supports extending from the lower wall and defining rocker support bores;
• a first breather passage defining a first inlet in communication with the rocker chamber and a first outlet that opens through the lower wall;
• a second breather passage spaced from the first breather passage and defining a second inlet in communication with the rocker chamber and a second outlet that opens through the lower wall, each outlet adapted for communication with a selected one of the cylinder assemblies, wherein when the rocker base is coupled to the first cylinder assembly, only the first of the outlets is in communication with the first cylinder assembly, and when the rocker base is coupled to the second cylinder assembly, only the second of the outlets is in communication with the second cylinder assembly.