Hi there. I have an 04 YZ450F and am pretty close to sea level, maybe 300ft above. I am coming close to setting it on fire. Here are the issues. I ride mostly trails, sometimes pretty tight, sometimes less. When ever cranking the throttle from 1/4 to anywhere past that, the bike always sputters for about 2 seconds, then takes off like a bat out of hell. That 2 seconds is sometimes all I have to accelerate before I need to slow down so it is slowing me down a lot. I was convinced it was too rich so I started to lean it out. I dropped the needle to the 3rd clip - that appeared to help a little, but it was still there. I then changed the pilot to a 42, it used to be a 45. No difference. I then changed the main to a 165, it used to be 168. No real difference. I have moved the fuel screw around and if I lean it out just a tad I get a hanging idle but no difference in the bog. It seems to be worse when the bike is very hot, say after a tight area, or after a lot of sand etc. I did the o-ring mod, felt a little better but at times will still bog just as bad. Once it makes it past the bog it pulls very strong, it is just a serious pain as it awalys first sputters, then flies out of the gates. I don't feel too comfortable dropping the needle any more. Any suggestions ?