The most reasonably priced component used on the Xt660r 2006 5vk6 Hungary 1e5vk-300e2 Valve is the Cotter, Valve.
A sample from the products for the Valve include: Arm, Valve Rocker, Retainer, Valve Spring, Spring, Valve Inner, Arm, Valve Rocker 2.
Check out any of the twelve Valve components enlisted.