I just took my new 1/4 scale extra 300s out for its 1st flight. Upon full throttle, the plane flies almost directly straight up. My elevators

and ailerons are adjusted properly, according to my previous flying experiences. Is this a problem with thrust angle or balance? I

believe the plane is correctly balanced.

Man I hate it when that happens on a first flight on an expensive plane
Doesn't really want to make you rush out and fly it again for sure.
Obviously the best way to tell would be to us an incidence meter, most can be used on the motor as well as the flying surfaces.
I guess you could level the wing with a small bubble level and then check the motor prop shaft with the level.
If it pulls to 90 degress that fast I would think that amount of upthrust would be quite noticeable.
If it appears close then go ahead and move the cg towards the nose. Maybe someone who flys one can speak up with some cg measurements for ya? Good luck

Tim

Check the incidence of the wing and stab. Both of those can cause serious pitch issues.

You don't actually need an incidence tool, although they're nice to have.

Prop the tail up so that the wing LE and TE are the same distance from the floor.
Now measure the distance from the Stab/elevator's LE to the floor and the TE to the floor.
Now check to see if the prop is at a right angle to the floor. (It's not actually easy to do that with the prop. It's much easier to use a flat piece of plywood or thin board bolted in place of the prop. Just drill a hole in a yardstick and use it instead.)
Take a look at the plane from the side and see what it's nose-to-tail centerline looks like to you. If it's not parallel to the floor......

What is the kit? ARF?