My lawn mower has a hard time starting up and staying on.?

We've had the mower for a couple of years and its starting to take at least 10 starts before it'll run without any choke. when it does, the engine oscillates in sound and dies when i push it over the grass. Its an older husqvarna mower from the 90's i believe. model # 96145001 if its any help. there was a long period of time where we didn't use it and it just sat around. Does anyone know what i could do to fix it? by "the engine oscillates" i meant that the noise it makes while running changes back and forth between a higher and lower pitch