I have a 1987 LT 500r and was wondering how much the power valve should rotate on its axis? 5°, 45°, 90°? I know that at 4500rpm the power-valve should rotate seen though the sight glass on the jug. I have seen virtually no movement. The quad is not sluggish just a little raspy at the top end. This leads me to believe that the power valve has little effect on performance. It doesn’t make sense to me. I would think it would run like crap. Any comments are appreciated. Thanks

 

I had an 89 500, The valve stuck open all the way when the engine was running even at idle , I had to adjust the spring tension to only open at higher revs. It made a huge diffence in power. My memory is kinda vag but i think it turned 90 degrees. Take that cover witht the four bolts and make sure it rotates by hand. Hope this helps.

 

Sometimes when people rebuild the top end they forget to remove the power valve linkage before lifting the cylinder and "jam it", remove the plate over the site glass and verify free movement.