I'm starting to tear down and hopefully re_build a 2104 YZ250F. I'll post photos and issues in this thread as I go. It had a cam bushing failure and filled the motor up with metal grindings. Besides the cam bushing there are some things I see after removing the head and accessing the crank timing chain sprocket. 1. Intake valves have come so close to the head there is no room for even carbon build up. It looks like there has been some very slight valve to piston contact. Notice the dull carbon on the ex valves and the more burnished look to the intake valves. ValveFaces by dbur971, on Flickr PistonTop-1 by dbur971, on Flickr PistonTop-2 by dbur971, on Flickr The compression was good before tear down, and the valves look OK with the solvent seepage test. After ~1min there is just barely any solvent film visible around the valves. Think these valves are OK to use? 2. I can feel a little roughness and stickiness in the can chain drive teeth. The crank sprocket shows some signs of stress, though all teeth are intact. CrankSprok-3 by dbur971, on Flickr CrankSprok-telecentric-1 by dbur971, on Flickr And here's a special treat, sprocket in stereo! View as cross-eyed stereo. look at the left image with your right eye and the right image with your left eye. Google 'viewing cross-eyed stereo' for some help with this. Can take some practice. CrankSprokStereo by dbur971, on Flickr Would you say this crank is still good to use or not? Follow the flickr links to see more details if you like. Thanks!