If you’re having a problem with your Trex 600n starter cup spinning on the starter shaft then this one is for you. At some point along the lines Align redesigned the 600n starter shaft and the problem is they didn’t cut the detents for the two set screws deep enough into the shaft. When you tighten down the starter cup with the set screws they simply can’t bite into the shaft enough and will cause the starter cup to spin on the shaft. The fix is quite easy. Simply take a dremel and cut-in larger flat spots on the starter shaft where the small circular detents are. Don’t be afraid to dremel in too far. This will give the set screws more “bite” and prevent the cup from spinning with even the largest of nitro motors. – Nick