Need to check your impulse grommet to make sure good. Good time to check the little rubber intake boot too.
Page 3 in IPL http://s30387.gridserver.com/partsDiagrams/Husqvarna 51 and 55.pdf
Page 3 in IPL http://s30387.gridserver.com/partsDiagrams/Husqvarna 51 and 55.pdf