My 250 would do the same thing, blow black watery crap out the pipe and all over everything. I keep leaning it out till it started to run rough. Then I stepped it back up till it smoothed out. The black crap went away. I never did look at the plugs, I new what they would look like. By raiseing and lowering the float, you can make a drastic change in how it runs. The Idle screw also changes how it runs. The idle curcuit is always working even with the carb open. If idle is to lean or rich, it affects the rest of the carburator and how it runs over all.
How does the exhaust smell, fuel or oil burning. You can control the fuel part. If oil burning, you can live with it or put money into a rebuild. The hotter heat range will keep it on the road for a while. Try one or two ranges hotter. If this a parade type non working truck, you won't have any problems. Joe
