A wise mechanic once told me "If it has ignition,carburetion and compression
it HAS to run. If it will start and run a bit several times, ignition and
compression are off the hook. Tillotson AJ 8 A or B carburetor is a zinc
die casting prone to corrosion if left exposed to moisture especially
the small interior passages. Carburetor with pitting and white powdery corrosion is a poor bet...on the other hand a carburetor showing the yellowish tinge of factory anti corrosion/sealant is almost certainly good and may only need a kit and some spray can carburetor cleaner followed by compressed air if you have it. Installing a filter in fuel line is not a bad idea either. In tank filter may or may not function...may even be plugged
a long soak in lacquer thinner if suspect.

Poor compression may be due to stuck rings which may respond to spray
tune up or not. The other option is tear down of power head...something
you probably can do but would rather not at this point. A fellow I met at
a meet shared the opinion that after 50+ years the old Kiekhaefers need
to be torn down, parts inspected (replaced as needed) and assembled with
new rings, gaskets and crankshaft, driveshaft and water pump seals...a
good repaint and decals to top things off. A NICE original motor should
not given full cosmetic treatment but may still need the tear down if it is
to run at its best.

50% of a tear down is stuck fasteners and crud, 30% is cleaning parts of paint,crud and old gaskets. Painting,reassembly and adjusting is the least
difficult part. Prior mechanical work may show up as missing fasteners,
electrical tape wrapped ignition wire, wrong spark plugs, and damaged
parts...good work leaves little to show it has been done...poor workmanship
leaves a broad trail.
Louis