Mower starts, but the chock seems on. Will only run with choke on. When I back the lever to idle, the mower chokes. I can't seem to figure the linkage out.

That sounds like fuel starvation. You probably park this for extended time with fuel in the tank. You probably have varnish buildup in the jets causing a lean condition. Few ways to solve this. Take it apart and clean it.. or put the right additives in the fuel and run it. I am a HUGE fan of BG44k, its expensive but is worth every penny (put half can in your tank and fill it up... let it run. Put the rest in your car, let it do its magic there too. Or you can get a can of Seafoam and do the same... not as good, but it works too. If that doesn't work, you can tear it apart to clean.