Some Basic Facts About Sparkplugs in the Modern Fuel Injection Age

I still see people talking about reading sparkplugs and doing plug chops etc on current sportbike forums and it just blows my mind that anyone thinks that kind of information is relevant. Plug Chops have always been sketchy for use with 4-stroke applications except in very broad troubleshooting terms and with the advent of fuel injection they are absolutely worthless.

Sparkplug readings are a thing of the past when you have fuel injection that can basically bypass the physics of Constant Velocity carbs in that with fuel injection you can make the engine run any A/F ratio you want at any rpm or throttle positon etc regardless of velocity of the intake charge.

The only way you can properly tune a fuel injected motorcycle is with the aid of a quality lambda sensor. A fuel injected bike can easily be rich at idle and leaner at top end (or vice versa) and you cannot tell which is which from looking at the plugs period. In fact you could for the sake of argument have a perfectly optimized map throughout the entire rev range except for the idle speed and nobody here could tell you otherwise from looking at the plugs. You could even have a rich condition that exists up to a certain temp during the warm-up cycle that disappears completely during normal operating temp, but you would still have dark plugs all the time from that cycle. You can also have a perfectly optimized map at one engine temp and then it goes overly-rich when the engine temp reaches another temp. The possibilities are endless so stop trying to read your plugs by the color of them and get your bike professionally tuned. Pro Tuners know the rules of tuning and will adhere to them