I have a 2001 400ex that would not run at all, then i had the valves adjusted and then when it would run there was a little bit of a knocking sound, but someone told me it was normal for 400ex's so i took it out and the timing chain broke instantly. Then i ordered a new timing chain and sprocket cause the sprocket got messed up too. And after replacing the new chain and sprocket it started just fine except it had just a little bit of a ticking noise. So i turned it off and check the timing chain and it looked fine, so i didnt know were exactly the noise was coming from, sounded like it was in the top end. So i took it out again and the timing chain broke again, so somebody told me i should've replaced the tension aswell, and my cam was stripped thats why the sprocket would strip off and brake the chains. So i bought a new cam, with sprocket and chain, put it in time and everything and now it wont start, checked all the simple things, getting plenty of aprk, gas, compression, and when i put it in time its at TDC.