SPARK PLUG COLOR & The Full Range Of Jetting

[Jaguar]

Man, I wish I had a dime for every time I’ve seen someone reference spark plug color in a way that indicates they think getting the color right is all that’s needed. It’s not. That color only indicates how the jetting is for the RPM range you use the most. For most people that is high RPM which means it indicates whether the main jet is too rich or too lean. That is very important but having that correct does not mean your mid throttle jetting is right, or that your jetting off of idle is right, or that your idle jetting is right.

You use the whole range of throttle so you use all the jetting which includes the idle jet, the slide cutaway, the needle jet, and the needle. Most people can get the idle jet and main jet right but fail at everything else, and for good reason. I have tons of experience at tuning 2 strokes and yet for the life of me I couldn’t figure out what to do right to get the full range of jetting right on my Suzuki AX100 even though I fully understood the subject. Look at the chart below and you will see how everything overlaps so of course if it is any worse than being a little off then only a computer can figure it out. So I created my jetting calculator. Only with its help could I figure out what needle to use, what needle height is needed, and what slide cutaway was correct. Now that bike feels electric as I slowly open the throttle. Most bikes just have the idle and main jet right and so the owner, to subconsciously obscure the obvious lack of correct mid range jetting, just cracks the throttle wide open all the time, never gradually opening it.

To see info about my jetting calculator please go to www.dragonfly75.com/moto/carbjetting.html

[GOT WOODS?]

WOW! Tons of great info here! Thanks for posting this, it is a huge help.

[KDXGarage]

Yes, thanks for stopping by!

[Vossman]

You’re website is incorrect. If you buy OEM jets from Jets R Us you get OEM jets, they sell both but they are clearly identified on their website.

[KDXGarage]

Jetting is tricky enough already. Don't buy non-Keihin jets.

[Vossman]

Truth right there.