first thing i would do is check to see that the center spindle (where backing plate screws on) is rotating freely, if not the bearing is bad.you can also try to move the counterweight by hand, their should be a bit of resistance when you try to move it. but i would give mikes suggestions a try as it took me a bit to realize you need pressure for the machine to work properly. i have realized one flaw on the 7346/7424 and thats the top plate that holds the grease and gears in the plate has no gasket so when the grease heats up it will melt out and leave pools of grease/oil. i since then used some rtv to make a gasket and seems to run better, also helps to replace the grease that was lost(these pc's are packed with grease!) yes i went offtopic but still good info!