well there are a lot of things you can get rid of, depending on how much you want to change and spend but alot of it is free, compfusions motor mounts fix the belt eating problem and make life easyier on the crank.
1: remove the radiator and all the extra coolant lines that goes with it, dont just loop the lines or put a restrictor in it because it lets lots of coolant bypass the rear coolers thus making your sled run hotter,
2:change the air box the stock box is very restrictive and heavy, i have the fire and ice box with the windshield intake kit and the plenum offset kit,which is the box that i would recommend, because the guys at fire and ice are so easy to work with, and also because the box gets the air from up high and doesn't seem to have the problem with powder ingestion like my buddy slp box did,
3:you can also get a aftermarket pipe and can, can loses most of the weight but you can get some pounds out of the pipe also with a little hp. i just went for the slp can and not the pipe, for the price the pipe wasn't worth the gain, but then again if your looking to be the lightest it might be worth it.
4: remove all heat shields that are unnecessary like the one by the can and any other items that you can take off and replace with heat tape, like the shield in the can side side panel and remove the foam on the clutch side side panel
5" remove all under hood foam EXCEPT little pieces in the sides that seal off the area in between the hood and the curves in the belly pan, foam might not seem like it would be heavy but go soak it in water and see how heavy it is . also the plastic piece that directs air to your brakes, i removed that as I'm not usually doing more than 60 on the trails and didn't see a need for it and DONT remove foam that seals air box.
6: remove all idler wheels on the rails and replace them with ice scratchers, the scratchers make a world of different in hyfax wear and also i get a drop of around 15-25 degrees in coolant temp PER a scratcher on hard trails.
7: holtz spindles only lose you a pound or 2 but are mandatory for making these sleds steer easier.
8: i put slp powder pros on and love them in the deep powder , way better than the stock ones, also Ive heard sly dogs work well, but the simmons ski's dont work well with the suspension geometry. might loses a pound with ski's
9: i also added 3" handle bar risers doesn't drop weight but made the sled way more comfortable to ride standing up I'm a touch under 6' tall,
thats all Ive done to my sled so far dont have a weight loss number yet but ill weigh it today and see what it is it was 577with everything stock except slp can with 3/4 tank of fuel and full oil.
10: get a mountain fit lexan hood with headlight removed, very light and you can paint the inside of the hoods and make them look sweet. my buddy wyrider did that to his sled 05 900 and it looked great, just the little after market head light looked kind of goofy and didn't do much when it was dark. thats why i didn't do that but you can contact wyrider on this forum to see what it looked like, he has a smoke tint hood and had some guy paint it and it was aw some, but needs heat tape on inside of hood, he rolled his and the snow pushed the hood into the pipe and made a big bubble in the hood.
11: you can port your track and loose some weight there and when your in the powder it will lose any where from 30lb to 50lb of snow in your skid, did it to my Buddy's rev 800 144 to see how the track holds up before i try it
12: use slush buster under the tunnel in front of the cooler because alot of ice builds up there.
13 i also put better boards the get rid of the snow build up on the board which is almost mandatory on this chassis
14 i also put a tri city front bumper on which is lighter than the plastic it replaces and also makes the front bumper usable. also a #225 front track spring makes the front end feel alot lighter.
. hope this helps......Nikolai