If you are sure the carb has been cleane properly,You now need to look at the impulse side, this is the positive and negative pressure created by the piston riseing and falling, it will be fed through either a pipe to the carb, or throught a hole in the induction block, if this is ok, the next step is a pressure test of the crankcase, if you have a massive leak at one of the crank seals you will have no primery compression in the crankcase, if you have no way to test this replace the seals as a matter of course, there could also be leaks elsewhere,induction block/tube,base gasket etc.
Good luck.
Husqvarna man, December 2009