I just rebuilt my carb in my 400ex, bored 40 over and got everything back together but when I started it up for the first time it revved up really high and I had to hurry and hit the kill switch. Can someone please tell me what the problem is? I'm supposed to ride in the Morning. Thank you!

 

You have a lean condition, probably caused by an air leak in your intake between the carb and motor, exhaust, usually at the manifold, or even head gasket.

 

Adjust your thumb throttle to the left not the carb just the thing that goes to the thumb throttle