Nice vaulting for a 14-yr-old!
I agree with CoachEric's advice. In addition to what he already stated about what his ARMS should be doing, I'd like to add what his LEGS should be doing ...
Or at least his TRAIL LEG - his lead leg is good!
In the vid, his trail leg is just hanging there - rather than SWINGING. This is a passive phase that needs to be eliminated. Don't just let the trail leg HANG there while the arms (and inertia from the run) do all the work.
Instead of just "letting" things happen, "make" them happen - by forcing the trail leg DOWN and around as vigorously as possible, immediately AFTER the elastic stretch. This is what I call the DOWNswing part of the vault, and the faster (and earlier) you do this, the faster (and earlier) your UPswing will be.
The consequences will be astounding once he "gets" this!
He will no longer need to "pause" in any tuck whatsoever to give the pole time to roll to vertical.
He will no longer need to shorten the radius of the trail leg to get into the tuck faster. He will invert plenty fast enough with a STRAIGHT trail leg for the entire DOWNswing and UPswing.
And the UPswing will be so fast that he will literally FLY off the top of the pole.
That's the "
pop on top" that you're asking for - and this is how to get it!
p.s. This isn't easily mastered overnight. But if he works on this all year, his results by next August will be astounding!
Kirk