Incorrect Spark Plug Heat Range:
- The NGK DR8ES-L spark plug may be too cold for your engine. A colder spark plug can cause carbon deposits to build up on the electrode, leading to fouled plugs. Try switching to a hotter spark plug, such as the NGK DR7EA.
Rich Fuel Mixture:
- If your carburetor is running too rich, it can cause the spark plugs to foul. Check the carburetor settings and make sure the air/fuel mixture is correct.
Oil Fouling:
- Worn piston rings or valve seals can allow oil to seep into the combustion chamber, causing the spark plugs to foul. Check the engine oil level and look for signs of oil burning, such as blue smoke from the exhaust.
Ignition System Issues:
- A weak spark or other ignition system problems can contribute to spark plug fouling. Check the spark plug wires, ignition coil, and distributor (if applicable) to ensure they are functioning correctly.
Engine Overheating:
- Excessive engine heat can cause the spark plugs to overheat and foul. Make sure the cooling system is working properly and the coolant level is adequate.
By addressing these potential issues, you can likely resolve the spark plug fouling problem on your 1986 Honda 350 TRX. Remember that proper maintenance and adjustments are essential for optimal engine performance and longevity.
