I have a 2001 YZ426 that will not start. It is a friend of mines and we have been working on it for about a week. We have completely cleaned the carburetor, check and shimmed the valves, checked timing and reset it. It has fresh gas, good spark with a brand new spark plug, It is getting fuel all the way through the system, we can't see anything visually wrong any electrical parts. We have tried kicking and kicking, bump starting, pulling it. We have tried using a little starting fluid. We haven't got any kind double roll on the motor or any sign that the motor is trying to start at all. We don't know the last time it ran, He bought it from a guy who never got it start although didn't know what he was doing, and the same with the person before him. If you have any advice it would be very helpful. Were hoping to not have to tear down completely.