I'll take a shot at the 2 husq. Almost sounds like the fuel tanks are not venting properly. Slight neg pressure and fuel is hard to draw in to the carb. When a certain neg pressure is reached, the vent lets in some air and things are OK for a short while then repeats.
Pull the fuel cap and inspect the rubber seal. Typ these have a valve that lets in air but doesn't permit fuel to leak out. I had to replace this seal once on my string trimmer as the seal felt sticky. New seal and all was OK again.