Save Share. Spark plug heat range is too cold for the operating conditions. Check the spark plug and the ignition wire to be sure they are both properly functioning. A lean spark plug will have little to no color on the insulator tip. Check for faulty or sticking choke, overly rich fuel mixture, ignition problems, leaking fuel injectors, or spark plug heat range is too cold. Dry and Wet Fouling Although there are many different cases, if the insulation resistance between the center electrode and the shell is over 10 ohms, the engine can be started normally. Cause: Lead additives in fuel. Plug colors tell the mechanic how the engine is running and can be very important. Plus, using a spark tester is safer than grounding a plug. Appearance - Firing tip is damp with gasoline, usually the odor of fuel is present on the spark plug. With the explanations above for its extremes, the spark plug is a good indicator for smaller settings issues which then become less obvious. A light tan/gray color tells you that the spark plug is operating at optimum temperature and that the engine is in good condition. So you should check your plug often. Spark Plug Tuning - Light My Fire The Tiny Spark Plug Should Be A Big Tool When It Comes To Tuning Your Race Engine. The top of a new spark plug is covered in white ceramic insulation. Contact us and we’ll send over an electrician who can diagnose and fix the problem ASAP. The black spots (look like pepper sprinkled on the plug) indicate a little too much heat on the plug which causes detonation by having the heated plug fire off the mixture prior to the spark firing. It could have the tip missing or any of several other problems. Spark plugs in general are always a controversial topic – copper vs iridium, hotter vs colder, single or multiple electrodes, brand vs brand and plenty more. For many racing engines, spark plug color is a window into the engine combustion process that can be used for tuning. All voltages before the ignitions coils are good. As spark plugs grow older, they lose their sharp edges as material from the center and ground electrodes is slowly eroded away. Exposure to heat and combustion byproducts changes the colors on the various parts of the spark plug. Any resistance at all would mean the plug is bad. According to AA1Car.com, this occurs when the spark plug fails to fire… You can't be serious. Low Compression-- (See our discussion of engine diagnostics for a compression test procedure.) For a two-stroke engine, having a fresh spark plug is incredibly important. i took out the spark plug and checked out the color of the spark because my bike is hard to start and i heard that blue spark is good and yellow is bad well mine is yellow and i think it is because i put low octain gas in the first time riding . See if you get a spark from the spark plug. A plug that has racked up miles should have a brownish or grayish color on the insulator and electrodes, but some gas additives have been known to turn fresh insulators blue, pink or purple. Single Fire - Single Plug: .035 to .040 Single Fire - Dual Plug: .022 to .025 Dual Fire - Single Plug: .035 to .040 Dual Fire - Dual Plug: .035 to .040 - When wired so each coil fires a plug … ... which can have a greenish color. Because of this, the tool provides an accurate measurement of whether there’s enough spark to jump the plug gap. New spark plugs should be able to fully burn all of the air and fuel mixture in the engine cylinder and little to no carbon buildup should continue to occur. Like many automotive components, spark plugs don't last forever. If a spark is present, the spark plug is working properly. The color should be read by looking at the porcelin insulator and compared to the plugs shown on the next few slides. Ignition system problems causing a weak or intermittent spark. 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