Black smoke at dawn

[Bernard]

Ole Harley Earl ('49 Super) smokes black and idles unevenly ("rump rump rump") during first warm-up each day, then runs sweet and smooth as molasses as soon as it gets going. I have to hold the choke fully closed and start from under the hood the first time I crank it in the morning, and with that it starts immediately. Choke is one problem, and I understand that--but the "loading up"--is that likely to be a float level problem or what?

Harley has new plugs, wires, and points. Gas mileage is down about 10% to 20% from before this black-smoke thing started.

[rcull]

I think before I got too excited about float level, I would try turning the choke back a point at a time and see how it behaved each time for a few days.

[Bernard]

. . .I've tinkered with the choke, but because I have to manually close it to start the car, I thought that wouldn't be the cause.

However it occurs to me now that there are very light springs here and there on the choke linkage. Could one of those be designed to hold the plate closed when no air is passing through, but open to the dial setting with air flow? If so, an explanation could be that the light spring is weak and the dial is set to rich.

Whatcha think?

[Jim Carmichael]

The way the choke works is a thermal spring closes it, then when the engine starts vacume pulls the choke partially open. To correct Harly's problem remove the choke cover while noting the position relative to the carb body, spray with carb cleaner while moving the choke open and closed. Spray around the choke plate and note the linkage on the end that connects to the vacume cylinder, spray the cylinder area and when everything moves freely put the cover back on but don't tighten the screws all the way. Rotate the cover until the choke just closes and test by pushing the plate open then watch it snap shut. It should close fully and firmly but not too tight. At this point you should be close to the original setting but don't worry if it's not as spring tension changes over the years. Tighten the covers fully and enjoy a properly functioning choke unless the heat tube running to the carb is plugged.

[Great Balls of Fire]

Check your manifold vacuum pressure. could have a leak when cold?