Bought these along with suggested spring kit in April of 2013 only rode 27hrs and now its time to replace already. I don't ride hard and only ride in the woods so I am not bouncing off rev limit or anything. Just poor quality valve.
Kibblewhite intake valves are a great upgrade from your O.E.M. motorcycle valves due to their superior performance and outstanding reliability.
All KPMI Black Diamond™ stainless steel valves are impregnated by a special German process to a depth of 0.002", with a surface build up of 0.0002". This "Black Diamond™" process improves wear properties, reduces friction, and provides resistance to corrosion and wear that is superior to chrome and nickel electrolysis plating. Each valve is designed using Finite Element Analysis software, and profiles are tested on Kibblewhite's computerized flow bench. Black Diamond™ Valves are light, strong, one-piece forgings with profiles that provide excellent flow characteristics and will outlast titanium valves.
Notes: Kibblewhite valves are sold individually. The Kibblewhite Valve Spring Kit is recommended for use with Kibblewhite valves.