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Black Smoke

Black smoke is always associated with an engine that is burning a very rich fuel mixture or unable to completely burn a normal amount of fuel. Common Causes: Dirty air filter Worn or fouled spark plug Improper carb adjustment Trash in fuel system Weak ignition spark If this situation occurs only when you accelerate the engine or when you first put the engine under a significant work load, there is probably no reason for concern. It is normal for the carburetor to richen the fuel mixture under these conditions. If the engine is running too rich under normal operating conditions, you will notice a significant reduction in performance and/or excessive fuel consumption. Quick Checks: Check to make sure that the air filter is clean Check to make sure that the spark plug isn't fouled. Verify that the choke control is in the off position and do a visual inspection to see that the choke valve is fully open on the carb. Adjust the linkage if required. If none of these steps indicate a problem, you may need to make adjustments to the main jet (if adjustable) or clean the fuel system and carb. Don't overlook the possibilities of a weak ignition system, especially on older point style engines.