I'll let you in on a secret...a bone stock 85-86 250 that's been tuned and running good has more power than anyone has the balls to use on a jump.
That is, on a naturally occurring dune, not a calculated exhibition jump with school buses, sparklers, flaming hoops, and a landing ramp.
Most jumps on the dunes don't require that much horsepower unless you're trying to jump Olds Hill or something, and if that's the case you should probably join the Nitro Circus.
For the most part, a sane jump on a dune is only going to be in 3rd gear or lower, depending on the curvature of the dune itself.
A long, sloping hill takes more speed to get airborne, but doesn't require much throttle because it doesn't rob HP like a steep dune.
A steep dune, especially one with a razorback on the top, is a lot easier to get airborne from, so less speed is a necessity (that also means you'll be in a lower gear with more grunt to make it up).
If it's a smooth approach to the dune, a blaster can keep up with an LTR if you're tough enough to land the jump with a crappy suspension.
I've out-jumped guys on 450's and craptors with an LT230, just had to take a little longer run to the dune.

Rule of thumb...if you can force the quad to wheelie in 2nd and 3rd gear by shifting your weight and gunning it, you have more than enough power to control the quad during a launch.
You're better off thinking about a suspension to soak up those landings and frame reinforcements instead of pursuing more power if you're interested in getting airborne.


My 87 250 was demolished from jumping it so much, the tubing underneath the swingarm/engine pivot point broke in half, then my pegs were the next part of the frame to go.
If I had been standing up, my foot would've wound up underneath the axle when I landed in 4th gear.
It was so out of shape and out of square that it was rendered scrap...I've cut it up and used the pieces to fix other frames.
Gusset, reinforce with additional tubing, get yourself a solid shock bridge for your frame, and upgrade or strengthen your swingarm along with suspension upgrades and you'll be much better off.