Hi,
You can look at the electrical system and it can help you identify the decade the Cub was made, if the electrical system is original.
A 1948 Cub electrical system is originally 6 volts, positive ground, with a starter rod that you pull to make the starter work.
The generator is sealed, and has a cutout, or Relay IH called it, on top of the gen. They have a 4 position switch on the dash that controls the gen charge rate, and the lights.
A 1948 Cub came with a magneto.
A 1970 Cub is originally 12 volts, negative ground. The starter has no rod that you pull. They had a push button on the dash.
The gen is open, or vented, with a fan at the front, and a voltage regulator on a bracket beside the gen.
They have a 4 position switch on the dash that is for the lights only.
Below is a page from the 1949 Cub owner's manual, showing the electrical system with the hood off.
http://farmallcub.com/rudi_cub/www.clea ... age-33.jpg
Below is a page from the 1965 Cub and LoBoy operator's manual, with the hood off.
http://farmallcub.com/rudi_cub/www.clea ... age-26.jpg
The engine serial number is stamped on the engine block, and can help identify the year.
It is not the same as the tractor serial number, except for the first Cubs, in 1947.
The engine could have been replaced, then the serial number would probably not be the same as originally.
Below is a page from the 1949 Cub owner's manual, showing where the engine serial number is.
You may need to clean it, and use a light to see it.
http://farmallcub.com/rudi_cub/www.clea ... age-02.jpg
If it doesn't have good power, it might need a full tune up, and the ignition timing checked.
The timing is important, if it is set wrong, the engine can have less power than it should.
You could do a compression test, and see if the compression is good.
