you think its your jetting its not. maybe the 400 is modded but your friend is liying to you. and yah i start in 3rd im 130lbs i can start in 5th on pavment with 4psi in my tires with holeshots and still spinn them. but you should feel if your clutch is slipping by cruzing in gear and flooring it and if you dont have any pickuo or its slacking and the motor reves up a bit before you take off its your clutch but yah tire diffrence matters. if he had paddles on sand and you have razrs your loosing. practice your driving your quad shouldnt be lossing. and switch bikes like someone else said that should be intresting