Hello everyone, I recently disassembled the top end of my engine on my 2004 CRF250 (Following step-by-step directions of a Clymer manual ofcourse) Before I decided to do work to the bike, it was extremely hard to start. I also felt like I had lost a great deal of horsepower when I was riding. Since I already have the head off, I planned on replacing the Piston, Rings, Pin and Clips. I don't take my engine apart often. I also wanted to replace some parts in the head such as valves, valve springs ect. The bike is 7 years old and I bought it used, so I'm thinking it's time I replace some parts. The last mechanic I took this bike to ripped me off, so this time I'm doing this job myself. I have successfully rebuilt automobile engines and I don't doubt my own work. I created this thread as I'm just looking for advice, tips, knowledge or anything else along those lines. *KEEP IN MIND, THIS BIKE IS A 2004, and I have never touched the top-end. I bought it USED in 2006. So today, when I went to check the valve clearance of the Intake Valves, the clearance was 0, as I could not fit any size of the feeler gauge in between the cam lobe and the valve lifter (intake side) The question I have for you all today is this: Should I replace the valves? Should I replace the valve springs? Would you recommend installing the OEM stock piston and parts or going with an aftermarket high compression piston? If I installed a high compression piston in this bike, what other modifications or adjustments would I have to do? What other parts in the top end of the engine would you recommend replacing? Below, I've included pictures to give you more of an idea of what I'm dealing with here. Here is a picture of my piston as it currently sits in the bike. Thank you all for your input. It's greatly appreciated.