That would be a good idea, but I have a couple problems with that. I race motocross, and have started racing on the national level. A 400ex engine cant quite keep up with the 450s no matter what you do. I was able to at first but now they have learned to ride. A 440 kit is a mid-range motor. My 400 was stock bore with a 11:1 sparks piston. It outran 440s and 450s through bottom end, which is what i needed for the motocross races. The bigger the bore the more I lose on bottom end and gain on top end. Even with a bigger bore a 400 wont catch a 450. Thanks for the help though. I appreciate it.