If you find the 05 onwards hit to hard , try a 03 powervalve shim , it makes it smoother at the hit. We modify these motor not only for more hp , but a broader , easier to use powerband , with the right mods , these are good engines , we try different mods as we can afford them , with 8 kxs and 2 klx bikes its a balancing act who gets the most money thrown at them. So much to do with so little money.