It died in the air while on a track. I nearly ate it hard. But the question here is why did it happen? To continue further the bike would not start at all after it happened. I have a theory, tell me what you think. First, to start, my bike is a 2002 WR426. In wanting auto-decompression I had posted a few times on here trying to find the best solution. It was determined that the Hot Cams would likely be the best solution, but I wasn't able to afford them both. Since the exhaust cam was the only one I needed for auto-decompression I was just going to get that hot cam when it was suggested that I get the OEM 03 YZ Exhaust Cam. I did just that, and installed it exactly one week ago. When doing so, I compared the new cam to the old one and noticed that the teeth were just slightly different. I read up on it online and confirmed that was what I should find and that I shouldn't worry, all would be okay. I finished the install and took it out for a good desert ride on Labor Day, doing around 50 or so miles. It worked like a charm, and I was very happy about it. In preparing to go the track today, I fired it up last night to warm it up. I heard a sound coming from the top end that sounded very much like a gear jamming in a car with a standard transmission. However the sound was very quick and fleeting and it went away and I didn't hear it again. At the track today I noticed the sound again - right after start up when warming it up. Since it happened so similarly to the night before I just assumed that it had something to do with being a little cold. However I started to worry a little more when out on the course I heard it every now and again. I had already planned on taking the bike into the shop to get a stripped bolt replaced, so I figured I'd just take it easy the rest of the morning and then have them look at it. It got more frequent, until finally while in the air the sound came quite suddenly and loud and the bike died. When I kick it in an attempt to start it there is still normal compression and it turns over the same as before, but it doesn't respond at all. It acts like the kill switch is engaged. My theory is this - the sound I heard was the timing chain missing the teeth on the new cam and as a result it wasn't spinning right (the sound is also akin to the sound your crank makes when your chain falls off). The timing chain would get back on though, and the bike would resume. However it kept happening to the point where the timing became so off that the engine isn't receiving any air, so it can't fire at all. Is it possible I didn't tighten the chain tensor right after installing that would cause this? Or did I misunderstand and install a cam that just won't work? I took it to a dealer and would like to be armed with as much input as I can when they call. The guy there treated me badly and I could tell he is the type that thinks owners shouldn't mess with their bikes like I did (this is another story - but the short is I would have and should have left immediately and taken it elsewhere, but I didn't have the time), so when he calls I want to have as much info as I can to counter any condescending negative comments I suspect he'll have for me. Thanks for any thoughts/input.