Well i have decided to rebuild my 2004 xr650r... Im going to use the xr'sonly bigbore kit and i want to install 3mm larger intake valves and 1mm larger exhaust valves, i already have a hotcams stage 2 cam (loved the results) and an fmf powercore 4 muffler. I will also be getting the fmf header and want to know if anyone have done an engine similar to this and does it yield healthy results? (hp) Also I was thinking about shaving the head and having a port and polish done ?? i have heard of people having bad expeirience with this ?