The engine is revving so high that it wants to engage the clutch.
1. Check clutch to make sure that no springs are hanging and that your bearings are good.
2. Check Idle gap to make sure it is set to .5- 1mm and that the slide doesn't close all the way when you hit the brakes. if your idle setting is right. Fatten the bottom end needle to bring the idle down.
As a precaution I would check my entire fuel system.
What engine are you running?