So your chain needs to be replaced? What you’ll need:
1. Chain Rivet Tool
5. Chain Breaker Tool
If you replace your chain before its completely worn out, you're sprockets should be just fine. The old rule of thumb is two chains to one set of sprockets. Most of the bikes I see that are in need of a new chain have about 20-30k miles on the clock. Very rarely will your OEM sprockets be worn in that time. The only exception is aluminum sprockets, they should always be replaced with the chain because the aluminum wears much faster than the traditional steel sprocket, but I digress.
Chain breakers say that you can just install and twist and the chain will come apart. But that only really works on smaller chains. I've watched many chain breakers crumble when they are used to break a 530, 525 or even a 520 chain. Modern chains are so strong they don't come apart that easy.
You'll want to push the pins out the back of the chain. Grinding off the face of a link removes the ‘staked' portion of the pins making it easier for you to push the pins out. Once the old link is removed, the old chain can come off. Be sure the bike is in neutral and just pull the chain out and throw it into the garbage. Removing the countershaft cover is a good chance to inspect your front sprocket. The smaller front sprocket will wear faster than the larger rear sprocket.
Measure four times before you cut. If you cut the chain too short, you're up the proverbial creek and out the price of a new chain. If you are a wise chain shopper, you purchased a chain with a rivet style master link instead of the traditional, clip-style master link. Your master link most likely came with the link, four little o-rings and a packet of yellow lubricant. Then slide the link into the chain from the back. You don't want to press the link together too tightly! If you do, you're master link will bind. Your chain rivet tool will have a special pin that has a concave dimple in the end. You probably noticed that the pins on the master link rivet have little recessed dimples punched into them.
In the same way you pressed the chain together, you want to press on the lip of the link pins so that the tool pins mushrooms it. Too much force will, again, bind the link or damage the master link all together. Last, you'll want to adjust your chain according to your bikes manual, and lube the chain lightly. On O-ring chains, your lube provides cushion between the sprockets and the chain and protects the o-rings from o-zone, UV rays and other stuff. Also remember to lube your chain about every 500 miles or so, and to clean your chain with kerosene every 3000 miles or so for maximum chain life.
Once you are done, you'll have a brand new chain, stronger than the chain that came with the bike.
Dirt Bike Axle and Chain Adjustment
Executive summary about motorcycle Axle and chains by JC Hilderbrand
1. Axle prep
Once the wheel is ready to be re-attached to the bike, before inserting the axle, make sure that it is properly prepared. The axle should be cleaned of any grime and then coated with a fresh layer of grease. Most bearing grease will do. Force the wheel up tight against the adjustment bolts and tighten the axle nut enough to hold the wheel in place, but do not cinch it down.
2. Adjust the chain
Loosen the lock nut on the chain tensioner on each side of the swingarm. Once loose, thread the adjustment bolts in or out to reach the desired chain slack (out to tighten the chain, in to loosen it). Use the marks on the axle blocks to make sure both sides are equally adjusted and the wheel is square. Everyone has a favorite tip for the proper chain adjustment. We try to leave enough slack so that the chain is tight when the suspension is fully compressed.
3. Tighten the axle
Once you are satisfied with the chain tension, put a rag between the chain and sprocket on the top side of the swingarm. Rotate the wheel backwards to cram the rag between the chain and sprocket which forces the wheel tight against the tensioning bolts. Use a torque wrench to tighten the axle nut to the specified tension, lube the chain and go ride.