Can anyone help me with the tension of a head on a 2004 Yamaha blaster.Thanks  

20 foot pounds of torque.

tighten them like you would a 5 lug wheel on a car.
tighten the first one then skip across the wheel to the far nut diagonally. then the one next to that and skip across until you get all 6 tightened.
it has a copper gasket so it is forgiving if you don't get the torque pattern just right.