That's a rough-looking flywheel/magneto. What do the coils and contact points look like thru the slots? Don't get any solvent on them.
I'd replace the magneto minimum with NOS or a good used one.
If it isn't chunks of rust,just flaky,I would clean the gas tank with BBs or nuts and half full of vinegar, well-shaken. Some people use screws. Once the worst is out, then do a full soak in vinegar for a day or two. Rinse,repeat if necessary and follow up with a good coating of 2-stroke oil swished around inside the tank.
Then you gotta keep changing out a few paper-pleated filters until it runs clear .