Saw used with the wrong type of fuel
Correct fuel mix is:
Less than 60 days old
Oil to gasoline ration
1:50 (2% oil in the fuel mixture) for use of original Husqvarna 2-stroke oil (recommended)
1:33 (3% oil in the fuel mixture) for use of other brand's 2-stroke oil
Small errors can influence the ratio of the mixture drastically when you mix small quantities of fuel. Measure the quantity of oil carefully and make sure that you get the correct mixture.