I friend of mine e-mailed me this plug guide as I have a project bike in the garage that wont start without a spray of Start Ya Bastard, so I thought I'd share with you guys... Plugs Types There are hundreds of types, sizes and brands of spark plugs on the market, even so only a handful will work in your engine. As a general rule of thumb, use the plug as referenced in your bikes manual, (same brand and part number). Reading a spark plug correctly: There are two different main ways to read a spark plug. The first way is to just unscrew it out of the engine and take a look at the end of it, matching the chart below.. The second way is the same as except you go for a really hard high revving ride on the bike, pull over and then unscrew each plug to read them. (Just make sure you wear gloves as they will be very hot). A spark plug can easily and quickly tell you the condition of an engine (good or poor), how it is running ie normal, rich or lean. CARBON DEPOSITS Symptoms: Dry sooty deposits indicate a rich mixture or weak ignition. Causes misfiring, hard shifting and hesitation. Recommendations: Check for a clogged air element, high float level, sticky choke and worn ignition points. Use a spark plug with a longer core nose for greater anti-fouling protection. OIL DEPOSITS Symptoms: Oily coating caused by poor oil control. Oil is leaking past worn valve guides or piston rings into the combustion chamber. Causes hard starting, misfiring and hesitation. Recommendations: Correct the mechanical condition with necessary repairs and install new plugs. TOO HOT Symptoms: Blistered, white insulator, eroded electrode and absence of deposits. Results in shortened plug life. Recommendations: Check for the correct plug heat range, over-advanced ignition timing, lean fuel mixture, intake manifold vacuum leaks and sticking valves. Check the coolant level and make sure the radiator is not clogged. PREIGNITION Symptoms: Melted electrodes. Insulators are white, but may be dirty due to misfiring of flying debris in the combustion chamber. Warning
Thanks Chris, great chart for plugs and information is fabulous. Plugs tend to get a hammering and putting new ones in is essential to keep the bike running at it's peak. Your chart however is a great diagnostic tool, it tells us whats going wrong, I like it Cheers Phil
