Its accelerator pump leaked, which caused it to idle high, which caused it to fail the emissions test. Once I re-built the carburetor the engine has spec compression and everything else works well. That's not failure. The idle had been higher than spec, but not too high for NM to fail it, for 10 years. I should have paid attention and fixed it then. I'm lazy.
I don't know what you mean.
Mr @the_same_mountainbik wrote
It meets state requirements, not necessarily EPA regulations
I know that. I looked at the standards for new cars, not the standards on my test results, when I made that claim. On the occasion of my first test, in California in 1997, I noticed that it met the standards for cars (not pickups, which have weaker standards) all the way to 2012, the most-distant year in the regs back then.