I just purchased a 98 yz400f, it seems to lack low end torque and power, once its in the rrs its fine. I rode a 04 wr450 and the wr450 has much much more power on the low end. Is the power difference from the yz 400 that much less than a wr450. The yz400 doesn't seem to have much stuff. the engine is 6 months old built by a yamaha dealer so the compression and condition is near new. I am not sure if I should sell the yz 400 and go to a 450. What is the stock sprocket size? I know it has a 450 pipe on it, other then that I don't know if any other mods are done, but I don't know, this is my 1st 4 stroke, my last bike was a 2000 cr500.