Hello All I have just obtained a 2005 yz450 engine and would appreciate some sound advice. Can anyone suggest the best gear set for the 2005 yz450 for road racing/supermono? See www.tigcraft.com The YZ450 has 4 gears, and as per the other posts, i see that a wr or a yz426 5 gear set will go straight in, and i understand that the yz426 'box is the closest ratio box. Here are my stupid questions: 1. Is the yz400 gear set the same as the YZ426? 2. Anyone ever heard of a 6 speed conversion? 3. Cams - can anyone recommend some for road racing 4. Anyone have experience of a big bore conversion/stroker kit, from a point of view of reliability, and actual power gain. regards pbro450.