These are scanned in images of the reference pages from a book. Find your bike below and click to get the appropriate page up. On these pages are a cross reference for your chain, sprockets, battery, and spark plug.
Drive chains need a few types of maintenance. It's important to keep the chain and the sprockets clean, as any dirt on your chain will likely work its way into the chain and cause wear. Modern chains are internally lubricated, and have o-rings to keep the lubricants inside. The o-rings need to be kept clean, the rubber kept fresh and moist. The side plates on the chain need some lubrication. Finally, the chain itself stretches over its life, and needs adjustment from time to time.
Put your bike on the center stand. If your rear wheel is off the bike, you can pull the sprocket assembly off the wheel. It will just pull off, it's held on by friction with the rubber dampers, there's no bolts. Put the sprocket assembly back on the chain, and put the rear axle through it. Put the motor in neutral, and you can now easily move the chain back and forth. If you don't have a center stand, you can often place a jack under the rear shock linkage and lift the bike onto the jack, side stand, and front wheel enough to spin the rear tire. A half inch of clearance from the rear tire to the ground is plenty.
This is a quite messy job. If you get some spray shaving cream and rub it into your hands and wrists, it will seal your skin and pores with silicon lubricant. Later, when you're all done, this will make cleaning up your hands a lot easier.
Use a rag saturated with WD-40. Don't use gasoline, this will ruin your o-rings. Spin the rear tire slowly while holding the rag against the outer sides of the chain to get the worst of the dirt off. You can also use the same rag to get the grease and dirt off of the rear sprocket and the wheel rim. Now, spin the wheel faster and spray WD-40 directly into the links. This will clean out the side plates and keep the o-rings lubricated and conditioned.
Finally, when the chain is clean and lubricated with light oil, you can seal the chain with a chain wax, such as Maxima or Castrol. Or, you can use Bel-Ray Super Clean chain lube, which has a very good reputation on street bikes. I don't recommend other chain lubes for street use - they seem to pick up more dirt and just make things worse.
Your owners manual will tell you how to adjust your chain. The chain should have roughly 1¼" to 1½" (30mm to 35mm) play in it halfway between the sprockets. There will likely be a colored marker on your swing arm that tells you when your chain has stretched to its useful limit.
There are electric chain oilers available, but they're $100 - $150, and people who have them seem to have mixed feelings about them. Seems like a lot of complexity to me just to drip a bit of oil. The electric products below use piston pumps. This is unfortunate, as any lab rat can tell you this application is crying out for a peristaltic pump. Simpler, less noise and vibration, no moving parts contact the oil. But a bit pricier.
Most modern chains are endless - they have no master link. To change the chain, your owners manual will tell you to remove the swing arm. This is neither necessary nor fun. You can get a chain breaking / forming tool from J.C.Whitney or http://www.1888fastlap.com. Call them for a free catalog. I recommend the Emgo / Motion Pro tool shown above. To replace your chain, first break the old chain, anywhere will do. Tie one end of the new chain to the old chain using string or light wire, and pull the new chain through the countershaft sprocket. Pull the new chain about until the two ends are next to each other at about 2 o'clock on the rear sprocket. You'll have to loosen up your rear axle to accomplish this. Put the master link through the two ends, then use your chain tool to rivet the new chain together.
Get a section of 1½" PVC. Notch the end to fit your swing arm. Don't forget to lock your front brake first. Idea and photo by Paul Fox.
Your swing arm almost certain has chain alignment marks on the two sides. However, these are notoriously inaccurate. Much better is to either align your rear wheel using the string method (see Rear Wheel Alignment above) or prop up your rear wheel, and spin it a few times while sighting along the chain and rear sprocket. The rear wheel is aligned when the sprocket teeth stay centered in the middle of the chain.