How do I replace the chain?
There are three ways you can go about removing your old chain and installing a new one. The 'tool' method involves the purchase of a special tool, so is somewhat more expensive, but will make your life easier. People have been doing this without the chain tool for a long time, though, and it is not as difficult as it sounds.
Chain tool method
This isn't such a difficult task. You will need to buy a chain tool.
First, removal: Grind off one pin of the chain (or remove the clip and master link if you have a clip-type). It is always recommended to replace your chain with a riveting master link type.
You must grind the head off the pin, even with a chain breaker, or else you'll break the chain tool. If you aren't keeping the old chain you can just cut off the old one.
Press out the pin (chain tool shown here; most people can't remember how they did this before owning the tool).
With the pin pushed through (about 30 seconds of work with the right tool), the chain will just fall apart.
Pull the chain off. (With the bike in neutral, grab the bottom run and pull). If you're keeping the front sprocket, temporarily install half of the new master link with one pin on the old chain and one on the new chain. That way as you pull the old one off, you auto-feed the new one on. Remember, however, that it's highly recommended to change both sprockets with a new chain.
Remove the rear wheel and change the sprocket.
It's easiest to loosen the sprocket carrier bolts if the carrier is still in the wheel. You can also loosen these while the wheel is still on the bike.
Here the wheel is resting on two 2x4's, so the brake rotor is off the ground. Be kind to your rotor; they're 180 bucks.
Reinstall the rear wheel and adjust the chain tensioners till very loose.
Remove the front sprocket cover. Change the front sprocket. Clean up while you're in there. Crud build-up can shorten the life of your new chain and sprockets.
Run the new chain over the top of the rear sprocket, the top of the front sprocket, and back to the rear. Button up the front sprocket cover. Line up both ends of the chain in the middle of the rear sprocket. Sometimes it's cheaper to buy a longer run of chain (110 or 120 links), in which case you just cut down the new in the same way you removed the old. On the other hand, buying the right length of chain will create less work.
It's much easier to install the new master link if the ends are on the rear sprocket, rather than trying to do it with the ends loose. Clean up the end if you had to grind the pin. Then, install your master. The rivet type of master link is preferred over clip type because we've seen too many failed/failing clip style links to feel comfortable with them.
You use the chain tool to press the master in. The Motion Pro instructions are pretty clear on this. What you need to do is line up the master link side plate with the plates on the rest of the chain. Some people line them up by sight, or you can use a vernier caliper (~$10 at Lowe's, auto parts and hardware stores) to measure the distance between two plates elsewhere on the chain and press the master to match. In other words, keep the same distance between the side plates on the adjustable master link as on links from another part of the chain. Be careful that you don't press the side plates too far with the chain tool. Check that the master link moves freely where it connects to the adjacent links before you peen the rivets, or else you may have an insta-kink chain and have to do the master link work all over again.
After that, the rivets need to be peened. This is what holds your master link on. What you are doing is taking the links (rivets) that are in your master and squishing (mushrooming) the ends with the chain tool, so the side plate won't fall off. The "peening" pin of the chain tool kit has a rounded end, like a BB cut in half, that leads to the straight shaft. The master link has hollow pins. So, when you start squeezing everything together, the rounded part pushes the master link pins down and out.
This can be done by eyeballing; just look at the other links on the chain and match the width. If you want to measure, grab the vernier caliper again. Measure the pins when they're cylindrical, before you start tightening the chain tool. Then you tighten down the tool. This starts the mushrooming process. Quit peening when they have mushroomed by 1mm in diameter.
Then, just adjust the chain to specs... not only slack, but also the run. Check the run by measuring from the center of the swingarm pivot to the center of the rear axle on both sides. Make sure each side's reading is within 1/16th of an inch of the other.
The last thing is to make sure all of your fasteners are tightened to spec. Give the wheel a spin to make sure it spins freely. Then, go for a 20 mile ride, followed up with a rag wipe to remove the excess lube packed on at the factory. This will keep the chain from collecting too much dirt and needing cleaning really early.
The chain tool most often used by members is the Motion Pro Chain Breaker And Riveting Tool, part #08-0058. It's a little expensive, but if you're planning on doing a lot of riding it's worth it. Note that you don't have to purchase Motion Pro items from them; a quick Google turned up several places that were $10-15 cheaper.
A more heavy-duty alternative is the Motion Pro Jumbo Chain Tool, part #08-0135.
N250RC E-Z chain removal method
Would you save this chain?
Note: Obviously (but you'd be surprised) only use this method if you don't plan to re-use your chain.
Step 1: Procure a 4" grinder (Dremel).
Step 2: Cut through the outside link.
Step 3: Cut through the inside link.
Total time spent: 30-45 seconds.
Removing the swingarm
This is probably the least-used of the methods shown here. Buy an endless chain (without a master link), and drop the swingarm. If you've had the swingarm off before and are comfortable with the procedure, then this method of replacement may actually save time over the above options. You really should get comfortable with it at some point, since swingarm maintenance is supposed to be carried out every 6000 miles.
If you're using the remove swingarm method you can easily assemble the chain off the bike. All this requires is a new chain with master link and the tools to peen the link, such as a centerpunch and hammer, or just a decent ball peen hammer and something solid to put behind the back side of the chain while you pound on it.
This process is covered in the service manual, but the book tells you to pull WAY TOO MUCH stuff off the bike. Pull the left peg stay, countersprocket, left pipe, rear wheel, shock clevis bolt, rear brake caliper, and swingarm axle. Bob's your uncle. (We at FAQ don't really all speak Canuck.)
You don't need any special chain breaking or riveting tools; a dremel with a cutting wheel, two 2" c-clamps and 2 hammers work just fine. Getting a chain that is the right length will make things much easier.
There are a few disadvantages to this method. It takes longer and is a lot more awkward (though less so if you have a friend who doesn't mind the risk of having his fingers smashed). You can: bend the rear sprocket, knock over the bike, and take tons more time trying to get everything together.
Take off the front sprocket cover so you can get a good look at how the new chain should be threaded on. Use the dremel (bolt cutters, hacksaw) to cut off the old chain, as long as you are just going to throw it away. It will help to remove the left exhaust canister, if you have one.
Loosen the rear axle, put the bike on its centerstand, and kick the wheel forward (after loosening the swingarm adjusters and rear brake torque link). Put the new chain over both sprockets, and bring the ends together under the top run. Grease and assemble the o-rings and master link.
Hopefully you got a riveting master link, and not a clip-type link; the clip-type is fine, but more likely to fail spontaneously (not likely to fail, just more likely). Both are assembled similarly, using the c-clamps to compress the link and plate. Using one c-clamp per pin, put the flat side of the 'c' against the far pin (the one that's already riveted) and the cupped side of the 'c' over the pin that you're pushing through (so you don't squish it as it gets squeezed out). Tighten each side one turn at a time until you just can't do it any more; at this point the clamp turn bars may be bent from the torque (!), and there should be a good one mm of pin exposed. Remove the clamps.
If you have a riveting master link, then take the biggest hammer you have and put it behind the link. Using a proper ball peen hammer (recommended; use the ball side) repeatedly hit each pin until it mushrooms out to about the size of the other rivets. It may take a while. If you have a clip-type link, use needle-nose pliers to carefully pop on the clip. Keep some spare clips on you, and check the chain at every gas stop. See the blurb below about clip-type master links.
Air chisel method
If you happen to have an air chisel handy, see here.
If you do have a clip-link chain, you need to take a step or two to increase its reliability. The first step should be to contact your local shop to see if they have a riveting link for your chain. Buy it and replace the clip one. If all efforts at this fail, you can safety wire it.
Specimen for dissection is a Parts Unlimited LM520 chain. Installed by the previous owner, a rivet link is not an option for this particular economy chain.
Get yourself some safety wire, in the range of .032", which is close to the largest size made. You will be using the safety wire to give your master link a better hold on the chain.
You should wrap the safety wire twice around the clip and the outer link of the chain that the clip is attached to. Make sure that the wire doesn't go past the inner links into the roller area. If it does, the sprocket will take it right out. Twist the wire and point the tail back towards the clip opening. Make sure that the tail of the safety wire, and the open end of the clip, face to the rear as the chain goes around. If they face the normal direction of travel (toward the front of the bike while on the top run of the chain) they are more likely to snag on something and fail.
In a pinch, safety wire will also allow you to get back home, should your clip come off. It fits nicely in the groove for the master link clip. Wrap it around the two pins that were holding your now-gone link and tie it off with the tail facing rearward. Check often. If your chain carries a clip-type master link, then you should carry a spare link, safety wire, and a needle-nose pliers.