I have a 2003 yz450f, I was out riding on my street today for like 15 min, I'm coming back to my house and the bike starts loosing power and dies. I assume its running out of gas so I cross my fingers and it fires back up, I have to keep feathering the throttle but it runs long enough to get home. I get back and check the gas its good, check the oil once it cooled down some and it was good, then the coolant again it was good. I spent about an hour trying a few things and couldn't find anything. So today I started taking it apart, I tore down the whole carb and cleaned it and installed a full rebuild kit(figured might as well while its apart). Then before I tried to start it again I pulled the valve cover and such off and checked valve clearances and all is within spec. So I get it all back together and same thing, it runs all choppy and i have to hold the throttle open some and feather it to keep it running and it will die under any kind of load. I have also checked and cleaned the air filter while the carb was off. I also checked fuel supply and it has a steady flow from the tank. I also pulled the spark plug checked it, and checked the gap (all good) Any ideas guys? I find it very strange that it started doing this all a sudden like this, the bike was not and has never been overheated or run low on oil, oil was changed about 20 hours ago with new filter and I cleaned the screen. Bike also has great compression......I'm lost.