While some might decry chain-drive technology as obsolete, that old link system is still light, compact and about as efficient as anything else. However, chains are also dirty, oily, loud, require constant maintenance and aren't the most durable option. It is primarily for these reasons that many enthusiasts pursue the quiet, clean efficiency of a belt drive.
If your bike has an external sprocket (mounted on the outside of the framerails) as most do, then the belt-drive conversion is fairly simple. Outside sprocket conversions are fairly straightforward and involve replacing the engine and wheel sprockets with toothed pulleys. Connect the two with a belt, install the outer case (if equipped) and you're good to roll.
Things to Consider
You can still retrofit an inside sprocket set-up, but you'll more than likely have to use a 2-inch (44 millimetre) or narrower belt. Although narrower belts are often a millimetre or two thicker than wider units, don't expect to transfer more than 100 horsepower without stretching it. Additionally, you need to bear in mind that a typical 3-inch drive belt system will add about 3.5 inches of width to one side of your bike. While this isn't usually a problem for choppers and cruisers that rarely see more than 20 degrees of lean, it's guaranteed to cause ground clearance problems for sport bikes/cafe racers that originally came with a chain.
Chossing a Type
Belt conversions come in three basic flavours: open-belt, enclosed belt and semi-enclosed drag-style. As the names might imply, the difference between them is whether or not the entire drive rides inside of an enclosed case. Open drives are lighter and easier to service, but are more susceptible to dirt, water and debris. While an enclosed belt might seem best for reliability, bear in mind that a billet drive cover will add at least another inch to the bike's width, and they are not cheap to repair if you lean a little too far. Drag-style drives use what amounts to a lightweight outer "girdle" or brace in place of a case, and are primarily for very high horsepower applications that need the additional bracing.
Kit instructions will vary by bike, kit manufacturer and belt-drive type. In all cases you'll have to remove the existing drive (of course), but you may also need to change out the transmission main shaft and bearing for one that will work with the pulley. You may have to move the transmission slightly, but your kit should come with whatever relocation brackets and spacers are required to do the job. Test fit the system repeatedly before torquing; the pulley's offset is sure to need adjustment with the provided spacers. When assembling, don't skimp on the threadlocker compound and make sure you use the right kind. Red threadlocker compound is the strongest bonding agent this side of a welding torch, which is exactly what you'll have to use later to remove anything you've sealed with it.