Hi everyone! Please forgive my long first post here. Typically Id hang around a forum for awhile before dropping an info bomb like this one. This is simply one of the most informative sites I have ever seen. From ghosting this place for 3 days, I’ve already accumulated knowledge that would take months on my own. (I am a 2-stroke convert. I have no problem with total rebuilds, but I need to bring myself up to speed on 4-stroke troubleshooting and tuning). I plan on hanging around for a long time, and maybe contributing someday... but for now: I need some advice on an 01 YZ426 with head damage I recently purchased. Here is a list of what I do and don’t know: I have no idea as to how the bike was maintained. This includes oil changes, valve adjustments, hours on the bike, type of riding, weight of rider. I think the bike was woods rode due to setup. I know nothing other that the condition of the bike. It is in poor condition, but it is due to neglect, rather than abuse. The rear sprocket is whooped out farther than I thought possible. I have to assume that this bike was neglected on filter and oil as well. However, the original cross hatch is still evident in the cylinder. I haven’t had time to mic it yet, but I certainly will. http://www.owlmeat.com/426.htm Ive posted a bunch of pictures on my website that may help explain what happened to the top end. Unfortunately I bought the bike after it was torn down. It appears that the valves were either floated, or maybe there was cam / chain / tensioner issues. Maybe the sprocket spun? In any event, the top of the piston contacted the failed valve 2 or 3 times violently, then maybe a hundred times after the damage was done. As you can see, only 3 valves look like they were damaged. Two bent, one broke. When I wiggle the c rod vertically, I don’t feel any play, and oddly enough it still feels smooth when rotated. I plan on replacing big and small bearing, as well as left and right, and getting the crank miced for wobble, just in case. The valve springs appear to be in good condition, but Ill replace those too, since they’ll be the last “old” thing left in the top end. Here are my questions to the pros out there: 1) What do you think happened to cause the initial contact? 2) What do you think is up with the small head damage that is on the valve side? 3) What are your gut-feeling chances that the crank is straight? 4) I don’t plan on it, but would you reuse the other two valves if they were straight? 5) I plan on trying to rebuild the head via Engine Dynamics or someone similar. If I stay with my current head, what years and models can I get valves out of? (I understand 2000 had steel, and I think 2003-5 are shorter, but what about a 250 model? Will those valves drop in? 6) Does anyone have a good reseller contact for Del West or blackdiamond / Kibblewhite valves? 7) If I can find the whole assembly (valves and all), will a 2005 450 head drop on my 426? (The entire low head design) This will probably need 05 chain and guides I guess. 8) Does anyone suggest machinists other than Engine Dynamics? 9) Is there anything I’m overlooking? 10) Got any extra parts? HAHA! Thanks to everyone!