Hi again. I posted something about this a while back. I haven't had any luck figuring it out and thought I would try again for any insight from others. I just picked up a lx865. It starts and runs smooth. As you throttle it up it runs smooth to about 3/4 throttle. Then it immediately breaks into a vibration and kind of a humming sound. If you throttle down it remains until you are a little less than 1/4 throttle. From there you can throttle up smoothly to 3/4 then vibration starts again. It feels like something orbital, that runs out of balance at 3/4 throttle and then will not re center until it slows to 1/4 throttle. The motor was removed and rebuilt by previous owner. I am thinking something in wing box or a hydraulic pump. I pulled the belt and ran it. Not in fan. Crank pulley not walking in and out. Motor does not seem to be source of vibration. Any insight on bad pumps or wing box issues would be greatly appreciated.