The carbon is because of an overly rich fuel-air mixture. Probably like Jerry says, you don't get it warm enough by not running it for very long. More time choked equals an over-rich mixture. The carbon in the hydro-carbon fuel doesn't get combined with enough oxygen to form CO2. The other side of the combustion equation is Carbon + Oxygen = Carbon Dioxide.


Kevin
1951 Chevy 3100 work truck
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1929 Ford pickup restored from the ground up. | 1929 Ford Special Coupe (First car)
Busting rust since the mid-60's
If you're smart enough to take it apart, you darn well better be smart enough to put it back together.