carb ?
 

so what is the trick to getting the slide rubber part to stay in place when putting it back together

The diaphragm? No tricks that I'm aware. Did you soak it in carb cleaner or another liquid? That can distort and mis-shape. If no, just keep seating the edge till it sits correct. Push it in around the seats edge till it lays in there without the need to hold any part of it.

Use a screwdriver to hold the spring compressed. I once used a little grease around the bead. But like Wolv says, its not needed if the part has it's proper shape.

Thanks no distorted shape just does not want to stay there was wondering about a little Vaseline was afraid it might distort it