I went riding yesterday with my buddy that has the 660 Raptor. We traded off and rode each others machines for a while. He seemed to think that his Raptor was faster than my bike. Honestly, I was scared to ride the Raptor very quickly as it scared me. When you hit the gas, it would take off in a different direction everytime. It "power-steered" under accelleration and it was never predicatable as to which way it would go. Anyway, we finally lined them up and raced. Each time he would get the jump on me as I had to control the wheelie action.. But I would quickly catch him and then blow past him with ease. No real comparison as it just was not much of a challenge. We rode about 60 miles in total. Towards the end of the day my bike started mis-firing under hard accelleration. It would not do it all of the time, but occassionally when running it pretty hard it would lose power, then pick right back up. No pop out the exhaust or anything like that, just an instantaneous loss of power momentarily. This was the first outing with the new 68S pilot, and the 158 main jet. I also swapped to a UNI filter which I purchased from XR's only. In case anyone is thinking about the UNI filter, it does come complete with the cage, ready to be oiled & installed for $28 bucks. I had a K & N but everyone said they flowed better at the expense of letting more dirt in. That is the reason that I changed them out. It seemed to perform pretty well. At the end of the day the bike was running like crap. It would not idle and kept stalling out unless you kept on the gas. Under acceleration it seemed to run okay but if you let off the gas you could feel that the engine was wanting to die as the compression braking felt like I was riding the brake.. If you pulled in the clutch-it would die instantly. Any ideas as to what I should check first? I was thinking perhaps the valves might be out of adjustment after all of the hard running, high speed, killer RPM runs I was doing. Tomorrow I will adjust the valves, change the engine oil, pull & inspect the carb to see if something is blocking one of the jets. The problem only seems to affect the first 1/4 of the throttle. I forgot to mention that I also turned the adjustment screw (wha'ts it called again?) in 1/2 turn at the beginning of the day and the bike ran well that way until it developed the problem it has now. I was thinking about turning that screw back out, but I don't think that is the problem as it ran all day that way and was not a problem until the end of the day. The bike will still rev up, but if you try to let it idle it dies, and under very light acceleration (1/4) throttle or less) it spits & sputters and wants to stall out. HELP! I have another riding trip planned for this weekend out in Highlands Texas and would like to have my baby running properly again. On a side note, I just purchased a complete aftermarket exhaust system with stainless steel header.. I will be installing it along with the Hot Cam as soon as it gets here.