It definitely depends on the bike and your weight. The key is to get off the gate straight and without spinning the rear tire too much. I was never more than a front of the pack C rider, but did pull 8 holeshots in a row in 1985 on a 2 year old stock 125. 1/3 to 1/2 throttle, smoothly let out the clutch, it should not be completely released until wide open in 3rd gear. On a 250, no more than 1/3 throttle waiting for the gate drop. In the C class it is easy to holeshot over 450 riders if you have the correct technique. I am a pretty timid rider on the track when it comes to jumps, I should move to drag racing!!! Another tip is if you don't have a full gate, try to pick a spot with no one on either side of you, hard to do in the 125 C class though!!!