If your crankset does not use rivets to hold the chainrings onto the spyder then you can do this mod by just getting some shorter single speed or BMX chainring bolts. Some folks have apparently had some issues with the chains falling off the solo ring but I've got a bike that I've ridden for years now that has not had this problem. Or if it has occured it has been so rare that I can't remember it happening.

How much lighter it makes the bike isn't much at all. You'll be removing only about a 1/2 to 2/3 of a lb at most. If your bike is one of the cheaper ones from the lineup that weighs in at around 30 lbs then you won't even notice the change. If you are enjoying your riding and still need to cart the bike up and down like this every day you may want to lighten your bike by replacing the whole thing with something that tags in at under 25 lbs. Along with the lighter weight you'll find that the bike is more rigid, spirited and responsive thanks to lighter wheels and a frame that is made from a stiffer and lighter tube type. All in all a nice bike compared to a lower end bike will make it feel like you've been working out at the gym for a month in a serious program...

In the meantime which model of Norco is it?