Hi I just recently purchased a 04 YZ450. My first couple of rides went great but today when I started it up and started riding I could tell it wouldn't rev up as high as normal. The only thing that I have adjusted on it is the idle because during riding when it would get hot if I just got off the gas and let it idle it would shut off. Other than that I haven't done anything to it. It is completely stock. I sat and let it idle for a few minutes and lowered the idle back down but when I would rev it up it would sound like it was hitting the rev limiter too soon. It also would do that when I would get on the gas while riding too, it would get up into decent RPM's and then start popping like it was hitting the rev limiter. Does anybody have an idea of what is wrong or what I could do to fix it?