Using your picture above, the faces of the cam, opposite your blue circle are critical. As the cam turns the cam follower on the bid rides up then drops that high point on the cam. That drop is what causes the tray to snap and move the coal up. You want both side of the bin to drop off simultaneously. On your bench, push the 2 cams together on the shaft and make sure that the drop off point on both cams are identical. Turn the shaft and do the same thing to the oppose cams. Also check that you have minimal play between the shaft and the cams; if the cams have a lot of play, you will get erratic operation.
Hope this helps.
