There are many reasons to change the winch cable on your ATV, including the risk of injury on old, worn out steel cables or worn out spots that may lead to breakage in the future. Changing the winch cable is not a complicated task, and it's a good idea to do at the first sign of wear or fraying.
Remove the cable that is currently on the winch. This can be done in one of two ways, depending on winch and preferences. One way is to put the winch gear in neutral so that the line can free spool, and pull on the clevis hook while walking away from the winch until all the cable is out. Another way is to put the winch into the "out" position and use the motor to spool the line off the drum. Not all winches have power-out options, however, so it may be necessary to physically pull the line off of the drum. Always wear thick gloves when doing this with steel cable because broken threads can cut hands very easily.
Next, unbolt the cable or synthetic rope from the drum itself. The end of the cable or rope will have a loop in it that is secured to the winch drum via a bolt and washer. The bolt is usually a hex head style and will vary in size from winch to winch. An adjustable wrench will usually suffice if the correct-sized socket or box-end is not available. Once the bolt and washer are removed, the winch line should fall right off the drum. Now is a good time to clean the drum, as well, if it shows signs of dirt or buildup. Then attach the new cable or line by threading the bolt through the loop and tightening down. For added security, a small amount of thread sealant can be used, but is not normally necessary.
Now, spool the new line onto the winch drum. Switch the winch to pull in like you would on a recovery, and walk the line back and forth along the drum to ensure that it wraps around the drum in a neat and orderly fashion. Not only does this save space on the winch, but it also guarantees that when the line is pulled out it will come free easily and without incident. Do not let the winch line wrap over itself or crisscross if at all possible. Once all the line is on the drum, secure the clevis hook and you are done.