I've got just under 43,000 miles on my WR250R. I decided to take the time to finally tear it down and go over everything this winter since I'm stuck not riding for the first time since I've owned a bike. I noticed my bike felt down a bit on power at the end of the season, so one of my goals was to do a compression check to see how healthy the motor is. Spec is 120psi, the gauge showed nothing more than 75psi. The motor cranks and runs fine and has never used a drop of oil in its life, but it has been dirtying the oil faster (in say 1000 miles versus the 2000-2500 it used to take for the shifting to get crunchy). When I added some oil down the plug hole, it spiked up to 100ish psi, so worn rings are likely the culprit. I ordered a new piston, rings, and wrist pin along with the necessary gaskets and a couple dozen other small minor maintenance parts I've been making do with. What I want to know is, how do I check the head, specifically the valve seats, valves, and guides for wear and what am I looking for when I have the head off to show that the valves need attention? How do I know if the valves are worn, if the seats need recut, if the guides need replacing, etc? I've only ever taken the head off one motor before (an old 2.5L turbo dodge that blew a piston) but never tried to do any work on one, so any advice is welcome and pictures definitely help.