Lawnmower running problem


Old 07-20-03, 02:19 PM
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Question Lawnmower running problem

When I start my lawnmower, it spits out some black smoke for a few seconds then runs like it has no power. It dies way to easily. I've tried cleaning the air filter, and replacing the spark plug, but neither really helped the mower with it's lack of power.

It's a craftsman 20" pushmower.

If you need more information on it, I'll see what I can do.

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Old 07-20-03, 03:30 PM
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Sounds like you need to rebuild your carburetor. Post the engine brand and all of the model numbers ect.
Old 07-20-03, 06:24 PM
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Hello Nemeknight. Welcome to our Do-It-Yourself Web Site and our Small Engine forum.

Based on the problem description, the engine isn't getting enough fuel after the choke opens. Very possbile the card is in need of an internal cleaning and new parts installed.

Check for a restricted fuel supply. This can range from fuel flow from the tank, through any inline filter, low fuel level in carbs with fuel bowls or a restricted carb of either bowl or diaphram type. Try using fresh fuel to flush out any stale fuel while checking fuel flow from the tank.

Also check the muffler for good exhaust flow. A damaged, overly rusted or excessively carboned up muffler may have internal damage causing an exhaust restriction.

Exhaust restrictions can cause several problems. Overall poor engine performance, excessive engine heat, failure to accelerate properly, hard starting, rough running and many more.

Engine overheating could be a factor. In order to remedy this problem, you'll need to verify there aren't any cooling air flow restrictions. Remove the starter housing cover off and clear out any debris under the cover, along the entire air flow path and on the cyclinder head.

Take a spark plug reading also. The plug firing tip should not be white. Slightly black, brown and or tan in color is fine.

Also check the heat range of the plug. Often this does not change the internal operating temperature of an engine. But be sure the correct type and heat range plug is installed.

If the engine is running too lean on fuel, this will also cause excessive heat. A spark plug reading will indicate a lean fuel mixture. See above.

You may need to richen up the fuel mixture some. Adjust the fuel mixture screw, on the carb body, a little by turning it outwards. {counterclock wise} The engine should puff out a tiny bit of black smoke. When a slight bit of black smoke puffs out of the muffer, turn the screw inwards slightly. {Clockwise}

Ideal fuel mixture is a mid point between too much fuel {Black Exhaust Smoke} and too little. Too little is when the engine just starts to die. The mid point between the two is ideal. Just slightly rich {1/8 turn out} is okay too.

For carbs with two adjustment screws, the screw marked "L" is the low speed fuel mixture screw. The screw marked "H" is the high speed fuel mixture screw. Both adjustment settings must be correctly set to avoid hot or lean running problems.

Incorrectly set low speed fuel adjustments {lean} will cause rough idling, stalling and acceleration problems. Incorrectly set high speed adjustments {lean} will cause excessive engine heat, poor performance and a lack of power, etc.

Other possibilities could be engine timing, especially if the flywheel was removed prior. Incorrect valve settings, an overly rich high speed fuel mixture {which would produce black smoke} or an engine running too hot caused by a lack of air cooling.

Small engine repair parts, generic repair manuals and additional help are all available at all local small engine repair shops and or lawn mower repair shops in your area. Shops and dealers are listed in the phone book directory.

Read the already asked questions and the replies offered in them on this same type of problem for additional help & information. Doing so will provide additional possible causes and the solutions to correct them.

If you need further assistance, use the REPLY button. Using the reply button moves the topic back up to the top of the daily topic list automatically & keeps all communications in this one thread.

Regards & Good Luck.
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