Remove the cover over the sprocket. There should be a screw that has a pin on it that fits into a hole in the bar. Turn the screw to move the pin towards the rear of the saw. You have moved the pin far enough when you can slip the chain onto the bar. Place the cover back on the saw and tighten the cover so the bar can still wiggle up and down. Turn the screw the screw to move the bar forward till the slack is removed. Put on some gloves and you should be able to move the chain around the bar. If you can not the chain is too tight.
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Remove the cover over the sprocket. There should be a screw that has a pin on it that fits into a hole in the bar. Turn the screw to move the pin towards the rear of the saw. You have moved the pin far enough when you can slip the chain onto the bar. Place the cover back on the saw and tighten the cover so the bar can still wiggle up and down. Turn the screw the screw to move the bar forward till the slack is removed. Put on some gloves and you should be able to move the chain around the bar. If you can not the chain is too tight.