i got a 1991 lt250 and my power valve doesnt always open just somtimes. Any problem areas that you know of?

 

It only opens at a certain rpm. I not for sure but I think its around 5000

 

Ive owned a 86 quadracer for a while and sold it because it was too unreliable. I just sold my 400ex and am getting a newer quadracer 87+. What exactly is apowervalve and what does it do? Is it a big improvement over the 85-86 engines without it?

 

Yes it is a big improvement. An exhaust power valve can be in several different styles, but the gist of it is that it changes your exhaust flow at various rpm. Opens up for more flow at higher rpm, less flow at lower rpm, giving more bottom power and more top power. Same theory in a (distant) way as variable valve timing in 4 stroke car engines that change the cam timing thru the rpm range.