Plug fouling


Old 05-26-02, 10:34 PM
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Question Plug fouling

The spark plug on my 2 cycle lawn mower engine fouls very quickly. It looks wet and has gummy deposits on the electrode. The engine is about 15 years old and has never given me problems before. Could it have ring or carburator problems, or is there anything else that be causing this. Any suggestions would be appreciated.

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Old 05-27-02, 05:48 AM
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Hello and Welcome wadesisk to our Do-It-Yourself Web Site and our Small Engine forum.

At 15 years old, the machine has served you well. Plug fouling most likely indicateds that there is plenty of wear on the internal parts. Depending upon what exactly is causing the plug to be wet is mostly likely do to worn rings.

Other possible causes could be an overly rich fuel mixture, too much oil in the fuel to oil blend ratio, a spark plug that's too cold in it's heat range, worn rotary valves or reeds, a plugged or restricted air filter and or wornout carb parts, restricted exhaust system and or muffler, etc.

To attempt to correct the problem, use an ashless 2 cycle oil per the oil manufacturers suggested blend ratio. Ashless 2 cycle oils cover a wide range of fuel to oil ratios, burn cleaner and with less smoke. These factors help to reduce carbon buildup and prevent spark plug fouling.

Check the heat range of the existing spark plug. It may be too cold a running plug, the incorrect type and or wornout. Replace it with the correct type and note the results.

Most likely I have not covered all of the potential problems. The other resident small engine service and repair professionals may offer additional suggestions, advice & help. Check back several times for additional replies.

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