Recently I talked about the problems I had getting my cam chain tensioner to properly tighten the cam chain during my rebuild. http://www.thumpertalk.com/forum/showthread.php?t=244895&parentpage=4 Well, I finally determined I had a bad cam chain and the new one arrived today. While waiting for the new chain to arrive I decided to finish as much of the motor work as possible and install the engine in the frame. I guess I forgot I still had to change the cam chain and that meant pulling the head (or so I thought). Today, I decided to try and manipulate the old cam chain off the crank gear even with the front cam chain guide in place. To my surprise I was able to move the front guide enough to get the old chain off and the new one on. I removed the two bolts on the rear guide and it easily moved enough to allow me to remove the chain there as well. Goody, Goody I successfully got the new chain on and got the cams timed. While I've still got a bunch of stuff to install before it runs I went ahead and tried kicking it over. It seems to work great. The new piston has all sorts of compression the the Autocomp feature works great and it kicks over like a healthy 250 two stroke. You may not think you have to install a new cam chain but after seeing these pictures, the facts tell me I should always replace the cam chain whenever I pull the cylinder for rebuild. Here are some pictures. This is the new chain and the old chain side by side. Notice any difference? http://www.bmnellis.com/images/yz426/camchain1.JPG Here is a closeup of the difference in length.....it's almost 1/2 inch even tho the #of links is the same. It just stretched which is why my cam hit the valves in the first place. http://www.bmnellis.com/images/yz426/camchain2.JPG Here, I've removed the old chain without removing the head. The rear chain guide bolts have been loosened and the guide moved. http://www.bmnellis.com/images/yz426/camchain3.JPG Here is the new chain installed before installing the bolts for the rear guide. http://www.bmnellis.com/images/yz426/camchain4.JPG Here are the cams installed and properly timed. http://www.bmnellis.com/images/yz426/camchain5.JPG The cam chain tensioner now tightens the cam chain just like it should. If I hadn't seen the difference myself I might not have believed it. Hope this helps.