1. Most centers have offset shafts in their ball lift links. “DO NOT” rotate the shaft to move the lift from side to side. Offset shafts were designed to allow for variances in the height or front and back differences in the machine alignment. If you rotate the shaft to center your lift you're not actually centering it, you're flexing the links and changing the angles of the pulleys. Doing this will wear the pulleys, drive you crazy with belts popping off and will wear and ruin the “V” of any ball lift belt over time. 

2. Before installing the lift, loosen the nuts on the offset shaft and drop the lift in place. Rotate the longer section of the shaft until the short section drops into the “U” mount. Slide in the clamping studs and slide the lift to center it. The long shaft should be level to the floor and squared off to the kickback of the machine before the nuts are tightened back down again. It’s easier to do this if you put each offset shaft in the links from opposite directions. The upper shaft should come in from the opposite side of the shock absorber so you have room to tighten the nuts. If you have narrow machines you’ll need to put both shafts in from the same direction to allow enough sideways adjustment room. 

3.No ball lift belt will pop off unless it first begins to twist. Stand on top of the machine while balls are coming up the lift and take note of any belt twisting. Slide the lift one way or the other until the belt stays centered. 

4. If you still have belts coming off check the side to side movement of the lift - something’s moving or the belt is not squared off to the up rails for some reason.