Well, I guess my streak of good luck with four strokes had to end some time. lol!! So, yesterday I'm racing at Glen Helen and the track layout is really long, fast and we were using three of the big uphill runs, one of which was pretty steep. We were doing fifteen minutes and during the last two laps of my first moto, my bike felt like it was losing power. No noises, it didn't lock up, it didn't skip a beat other than feeling sluggish. It felt lazy coming out of the turns no matter what gear I was in and I was down shifting to second at the top of the steep up hill I was hitting in third or fourth a couple laps earlier. It was still pulling fine on areas that didn't put a load on the bike, though. I checked the cam timing just in case that jumped, but it's still good. I rode it around the other track there before my second moto and it felt OK, but that track didn't have any hills I could check it out on. I didn't risk it in the second moto and borrowed another bike. Since then, I haven't done anything else. Looking to gather thoughts, suggestions and ideas before I start tearing in to it. Don't want to take things apart I don't need to. If someone has experienced this and found their cause, I'd like to hear what your problem was. So far, I've had people thinking crank, piston, valves or carburetion. First on my agenda is to drain the oil and check for metal. Oil is new with an hour and a half of ride time.