Ignore some of my rambling but read below from a post back a while ago:
Have you ever done carb work? If yes, then proceed. If no, drop the machine off and pay someone the little bit that it would take to go through them. If the the PO pulled them and "cleaned" them but did not set them up I would question the cleaning job. You would start with a full disassemble, check for bad or worn parts and clean them very well. This means all jets and passages (can gently heat up jets with a propane torch once removed and or use torch tip cleaners/wire strand to de-crud them). Once they are satisfactory reassemble and set float height. You should have no problem finding the carb specs for your machine online (though it may take some digging). Attach and adjust choke cables. Attach and adjust throttle cables/slides loose, as in freeplay (you will see why coming up). Now you will want specs. There is a spec for throttle cutaway - the amount the slide should be open at idle - as a baseline for adjustment. This is usually measured with a tiny drill bit. Set your slides with the idle screws so you feel slight drag on the slide moving the drill bit. Once you have ALL 3 set the same and are happy....re-adjust all your throttle cables. When you get ALL 3 cables adjusted, recheck your slides that they are ALL still sitting on the idle screws and they ALL open open evenly/smoothly. Once you are done here, provided everything else is buttoned up and up to spec, you should be ready to fire the sled up without the air box on. You will want to acquire a carb syncing tool. This goes over the throat of the carb and has a sight glass and a floating ball, aka a vacuum gauge. Fire the sled up and finely tune the idle screws so ALL 3 carbs are pulling the same. Shut off, re-install air box and see how your work turned out in the form of a nice unrelaxing, nail biting, I just worked for 3 hours to tune this piece of $hit and it still runs like $hit, test run! When you return, put an ad on your local advertising media of choice and buy something with fuel injection lol. Kidding about the last part and not at one point did I mention jetting and all of that spark plug reading, crank seal checking stuff that typically goes into this....so take it upon yourself to make sure the sled runs right and is in good mechanical condition to start with. Best of luck and remember, it's fun they say.