My chain saw is small—just a 12-inch bar—but it's perfectly adequate for thinning small weed trees out of our woods. I let pros fell the big trees, but once they're done, my little saw easily handles the cleanup, including cutting the trunk into logs for the fireplace.
Chain Check
Before using a chain saw, I always check the chain tension. If it's too tight, it'll wear out the bar and sprocket and can even snap. If it's too loose, it can jump off the guide bar.
First, I put on a glove so I can pull the chain around the guide bar. It should track smoothly and with little effort. (If it doesn't, the saw's guide bar may be bent, the sprocket in the bar's nose may need oil, or the chain may be too tight.) Next, I pull the chain away from the bar about midway along its length. The chain should lift slightly—about 1/8 inch—but the crescent-shaped drive links underneath the chain's teeth should remain in the bar's groove.
To adjust the chain tension on most saws, loosen the mounting nuts at the base of the bar, move the bar in or out slightly, then retighten the nuts. Once the tension is right, then it's okay to start.
