NEW PRO CIRCUIT TUNED AND PORTED HONDA CYLINDER HEAD ASSEMBLY. There is a fine line to building an engine. If the limits are pushed too far (like many engine builders do) there are reliability issues. Pro Circuit's goal is to give you the very best in high-performance service without any loss of reliability. Pro Circuit engine modifications will give you increased power from bottom to top! Pro Circuit has specialized in motor modifications since the early two-stroke Husky days. Our expertise in building the world's most advanced engines is a direct result of working with the fastest and most talented racers. Riders like James Stewart, Ricky Carmichael, Ryan Villopoto, Chad…