Do i have to mix 2 stroke oil on the gas for the 4 stroke bikes or just add regular gas on the tank? if is what is the scale for the mix?

DO NOT mix oil in the gas on your four stroke engine. You will foul the spark plug(s), build up deposits on the valves and head, and make a smokey, smelly mess. A two stroke engine uses the fuel/oil mix to lubricate the engine before being used as fuel. A four stroke engine has a separate lubrication system and does not normally burn any oil. As the name implies, a two stroke engine works in two strokes. The first stroke is downward, where the fuel/oil mix and air are drawn into the cylinder. The momentum from the crankshaft counterbalance or force from the other cylinder(s) drive the piston back up compressing the mix, and the spark plug sparks at or slightly before the top of the stroke. The rapid combustion of the fuel/oil/air mix drives the piston down, which is the power stroke, and then the cycle starts all over again. A four stroke engine has an intake stroke down taking in the fuel/air mix, a compression stroke up, a power stroke down as the fuel/air mix is ignited at or before the top of the stroke, and a exhaust stroke up before starting all over again. A four stroke is much cleaner and more reliable than a two stroke, but it is heavier and has less torque. A two stroke engine is much lighter and has more torque, but takes more maintenance.

That is great advice. I really agree, since it happened to me.