Slacken the bar nut/nuts, somewhere either on the front of the machine, or in the clutch cover will be a screw, turn this clockwise this will move the bar forward and increase the chain tention, some machine have a sprung loaded bar and just slackening the nuts will adjust it, some machines have an intenz bar, and the adjuster is in the side of the bar itself( a large screw driver slot) sorry to be so vague but there are many different systems out there.
Husqvarna man, January 2010
