That is the flatback carb with a primer pump on the side. The pumps are sealed and not rebuildable, they work or not and no new repacements have been available for a very long time.
If the saw starts well and runs good, I would change the fuel filter and leave it alone. If the primer pump doesn't you can manually squirt some mix down it till it runs on its own. Or you can convert it to a tillotson with a choke.
Dissasemble the carburetor and use spray carb cleaner and compressed air not a dip tank. Do not remove the sealed plugs inside it.