Weak ignition? Low compression?
The carburetor isn't the only thing that affects how they run, and it's not always an 'easy' or 'cheap' fix like suggested in so many sales ads.
It takes all of a few minutes to check compression, for real, with a real compression gauge, not just sitting an obese squirrel on the kick starter to see if it moves. Didn't move, passed compression test. Squeak, squeak.
You can find free manuals online. Definitely go through the specs, check things, then go from there. It'll save some time and give you some idea of overall engine condition.
The story of three wheels and a man...