8 N ford won't pull

Compression is a good question for any tractor.
Some things I've learned on my 8N over a few years:
1) Had a time when one plug wasn't firing (no spark), though it does not sound as bad as other machines who are only firing on 3...just wouldn't pull, so check each plug individually to ensure you're getting spark.
2) Fuel system seems to be the most vulnerable part. Plugged filters in either the tank or the carb can provide just enough gas to keep it running but not enough to run it well.
3) Carb assembly and adjustment; when I bought mine, I discovered that somebody had rebuilt the carb wrong and installed the choke plate basically backwards so it never would fully be open. Ran like doo doo until I found the problem.

There's other things, of course, but those are pretty well common to any engine. You might also try posting on the N-series site here at YT.

Good luck.
Tom

Good Luck
Steve