1. Make sure your airbox is on tight and there are no air leaks caused by a cracked carb. flange or a ripped airbox boot. Make sure your air screw is around 1 1/2 turns out. If you're having to choke it to make it go and the aforementioned items are deemed good, your pilot circuit has some restriction caused by debris. This is the most common problem to find. If you're getting a super rich condition with some backfiring out the pipe, and extreme flooding when the machine is off, you probably have a bad needle and seat assy.
Continue if cleaning is necessary:
2. Pull the carb out, take the bowl off and disassemble the carb down to the nuts. You can leave the idle screw installed. SOAK everything in parts solvent or carb. cleaner for 30 minutes. Don't just hose everything down with carb cleaner and call it clean. It leaves a nasty residue and just hosing a carb off won't clean it. After letting everything soak, use a toothbrush to clean everything thoroughly. You can buff the jets on a wire wheel if you'd like. **If you filled a container with canned carb cleaner, wash everything off in a bowl of dawn dish soap and warm water immediately after removing from the carb cleaner. This will prevent residue from forming** After that, dry everything well with compressed air. Make sure to blow out all passages with the air gun and verify that they are free of debris. Use a wire brush bristle to clean out all holes in the pilot jet until you can see daylight. Blow the jet out with compressed air. Once everything is clean, it's assembly time.
3. Assemble the carb carefully. Check float height as per the tech manual that you are no doubt using. Vacuum check the float valve (needle/seat) with a "Mighty Vac" brake bleeder or vacuum pump by putting the line on the fuel inlet nipple and pumping the vac up to 5lbs. It should hold that vacuum for at least a minute until it is deemed Okay. Check any gaskets, o-rings and/or fiber washers to make sure that they are in good shape and reusable. Assemble the rest of the carb and set your air screw to the recommended spec.
4. Set your choke as per the tech manual. Use a 3/16" drill bit as a slide height guide. Make sure that the drill bit barely rubs on the slide. Set your idle here with the idle screw and adjust the slop out of your cable(s). For dual carbs make sure that your slides are synchronized meaning that they will start moving at the same time and they will reach the top of the carb throat at the same time. MAKE SURE THAT YOU HAVE YOUR AIRBOX INSTALLED OR THE MACHINE WILL RUN LEAN!! JDs are finnicky and the 3/16" drill bit is the best baseline method I can come up with to get carb slides close.
This should help a few people avoid forehead bruises.
Remember, with today's gas...and JD gas tank plastic, it's imperative to clean your carb(s) every year on every machine that you plan to ride. With the needless addition of Ethanol to fuel, carbs are no longer varnishing over long periods of time; they are now after as little as 6 weeks staining green inside and given the right conditions and time corn will start to sprout. This is no joke. Make sure to run PREMIUM NON-OXY whenever possible to avoid dirty carbs and possible engine burn downs.~Jack