Seems a lot of talk and questions about this. Here is how I did this on my 96 Sportster 1200, but it should apply to most belt-drive evo Sportsters, with minor variations/part numbers.
There are companies selling "kits" and such, but ordering the parts individually should save you some serious cash, and it will also allow you to tailor your gear ratio and chain pitch to your preferences.
Here is what I used..........
*5-speed trans sprocket spacer HD #33334-85 ------------$20
*Mainshaft Oil Seal HD #12050 -----------$4
*Quad Oil Seal HD# 11165------------$3
*Renthal R3-2 O-Ring 520 chain X114 links --------$80
*48 Tooth 520 rear sprocket Chris Products (PBI ?)#205348 ------------$60
*21 Tooth 520 front sprocket PBI # 277X-21-----------$35
Total-----$202 shipped give or take
Note I decided to go with 520 pitch chain, not the standard 530. There are arguments on both sides for either choice, but I wanted the lighter 520 set-up. Also, your choice in front/rear sprocket teeth will be a personal choice. I ride in traffic a lot, not much freeway. So my choice was geared towards off the line acceleration, not low freeway RPM's.
Now you may be able to get that all for a little more or less cash, but this is what I paid...shipped. Got most of it through J&P, the chain through MCSuperstore, and the 21t sprocket on ebay. Your local HD dealer should stock the oil seals and spacer. Beats the hell out of the overpriced kit. You also will need:
*Red and Blue Loctite
*Chain Breaker/Riveter
*Misc. mechanics hand tools
*Jack
*Factory Service Manual
*Torque Wrench
*1-7/8" Socket for Transmission Nut. I did not have one that size, ended up finding an impact socket for $20 shipped through Amazon. (it's 3/4" drive as well, so be prepared)
This took me a few hours on a Sunday afternoon.
Supplies. (that little bag in the upper left corner is a clip-style master link, just incase)......
Put your bike with the front wheel up against a wall or something immovable. This is so when you are taking the nut off the mainshaft, it will give you leverage......
Take off the sprocket cover and bungee it up out of the way....
Take the lock ring off your old pulley....
No pic of the wrench and huge socket "in action", but I got my impact driver and took off the giant nut. It is REALLY on there. Remember, it is REVERSE THREADED! You can use a breaker bar and heat if you don't have a driver. I got it loose with the driver and finished up with my hand ratchet.....
Old pulley, lockring, and nut....
Bare mainshaft (still with the old spacer and seal).....
If the bike is not lifted yet, do it now so you can take the rear wheel off. I got one of these easy lift things that pivots on the swingarm. Makes maintenance much easier than using my clunky m/c jack....
Axle out, wheel off. Start taking off the pulley. 5 gallon bucket or milk crate are both good choices. While the wheel is off, you need to take off the old belt. You can cut it off in seconds, but I don't like wasting parts, so I choose to slip the right shock off and pull the belt....
New sprocket. Weighs less than a pound. Nice....
Put new sprocket on the wheel. Loctite it up. Torque to specs (55-65 ft-lb)....
The goods you need for the next step. New spacer, oil seal, quad-ring seal (looks like an o-ring), nut, and the sprocket. I ended up not needing the quad-ring seal (my old one was in perfect shape)....
A side-by-side of the old spacer and new one (longer).....
Here's how I got the oil seal out. Took a wood screw, and CAREFULLY screwed in just the tip. Gave me just enough leverage to yank out the old seal, without digging at it with a pick or screwdriver.....
Look at my balls...
Now, this is where you would put in the Quad ring seal. On the mainshaft, before the spacer. But mine was great looking still, and the new one I got was a bit flat on one part. I made the executive decision to roll with the old one.
New spacer going in. Bevel goes TOWARDS transmission....
I lubed up all the oil rings edges with wheel bearing grease, so it would slide in real easy. Then I GENTLY tapped all around the circumference with a soft rubber mallet.....
Put the sprocket on....
Now check alignment with something true. You can't have ANY deviation.....
Put your chain on. Get the breaker out, and line it up. Before you cut any off, adjust your axle so it sits as far forward as possible. Then line it all up, and decide how much needs to come off. Be conservative. You can always cut more later if you need. I went with 3 links. Making my bike 111 links total needed. Yours may vary......
Now, the Renthal chain uses a rivet link to close it off. I do not own a rivet adapter for my chain breaker, but it is simple to rig up something. Take a hard screw that will fit inside the hollow "pin-ejector" slot. Stainless works.....
Take the breaker and put it in the same way you would break a chain, and use the pin driver to stamp the head that needs to be riveted. The screw will keep the other side of the pin from backing out. Repeat on the other pin....
Starting to get there...
This next step takes a little balancing act. Put the nut on. Remember, turn left to tighten. Put the bike in 1st gear. Sit on the seat, and take your ratchet and start tightening. Get it until it's nice and snug. Then, take your torque wrench out, and tighten to 50 ft-lb.....
Now, follow your manual's suggestion on the correct process for setting the final torque on the nut, and also for setting the lock screw. As you can see, the PBI sprocket has a different locking system than stock. Here you have to put a small lock bolt on the flat of the nut, so it can't turn and back out. Don't forget loctite on both.....
The take-offs....
I dig the new chain line and overall cleanliness of the chain vs. belt. Note the timing cover. Now is a good time to set the proper tension on the chain, and fasten your axle nut and clip to specs....
And, the whole picture.....
Im curious what air cleaner that is 
Linear Mode
