two stroke plug reading 101
- Thread starter the gman
- Start date
M
This is my last plug reading of my 38mm smart carb. I run it down the trail for a couple miles at about 1/2 throttle and i'm looking for this color. After I get my low/mid fuel set right with the clicker I will do some full throttle long pulls and pull the plug again looking for this same color to see if the metering rod is correct. If its lighter richen it, and darker lean it. For initial settings in the garage I get it up to operating temp and whack it full throttle very quick, you want a clean acceleration and as the motor is decelerating on its own you want to richen it until it decelerates smoothly with no popping or nervous sounds if you let it off and it goes nah nah nah, its still lean. If it has an erratic idle its also too lean. If you whack the throttle and its too rich it will be slow revving and it won't sound crisp. Its kind of hard to explain but I hope that helps someone.
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P
I learned, reading only spark plugs is not a reliable way. Piston wash is much better, however that's probably impossible to do on a bike. Garry, save yourself all this stress and come back to the 4 stroke. 
Youre starting to remind me of your 09 Dragon days!!
Youre starting to remind me of your 09 Dragon days!!
M
Sounds of your bike while riding will tell you almost as much as reading your plug so try to learn what lean and rich sound like. When you chop your throttle and hear a little mis, pop or inconsistent sound you are usually lean, if it sounds like its not a nice crisp sound and you see blue smoke when accelerating its rich. Hopefully some on can explain that better. Lean will burn down the motor, rich just won't run that good, so caution on the side of rich when changing rods/jets. The smart carbs are a little tricky to tune as the clicker doesnt have any effect on full throttle, if you're running a metering rod that is too rich you could lean out the motor to the point of being able to burn down the motor running half throttle and almost flooding it out running full throttle. And if youre running a rod thats way too lean you could richen it up enough to hardly run at idle through half throttle and burn it up when you twist it wide open.
hey there champion
unless you'r are a card carrying tech staff member at champion or ngk you can't read a plug with the naked eye, or eye loupes, but maybe with a electron microscope and good schooling.
Well ok, maybe not that tough BUT.
2 stroke carb
2 stroke carb oil injection
2 stroke FI
2 stroke FI injection
4 stroke carb
etc
ect
All different plug readings
So when I handed a Champion tech my plug asking about my main jet he said my timing was about 1 1/2 degress too advanced, my oil mixture was slightly too rich, I had a little deto around 3800 rpm, would help to drop one tooth on my rear sprocket. Main jet was close. Plug was black.
So black or tan like dogs.......tells you something.
unless you'r are a card carrying tech staff member at champion or ngk you can't read a plug with the naked eye, or eye loupes, but maybe with a electron microscope and good schooling.
Well ok, maybe not that tough BUT.
2 stroke carb
2 stroke carb oil injection
2 stroke FI
2 stroke FI injection
4 stroke carb
etc
ect
All different plug readings
So when I handed a Champion tech my plug asking about my main jet he said my timing was about 1 1/2 degress too advanced, my oil mixture was slightly too rich, I had a little deto around 3800 rpm, would help to drop one tooth on my rear sprocket. Main jet was close. Plug was black.
So black or tan like dogs.......tells you something.
today my bike ran great all day spot on perfect especially above 9000 feet. plug looked brown, good enough for me. on the way down my buddy on a new ktm 500 xcw was getting all racy on me since I hurt his feelings up high booni'n with my blue killer bee! at around 6500 feet as I went 5th wfo on the trail near the truck I heard it ping for the first time all day looked down egt was at 1250. seems to be spot on accurate. Anyway like mx'er says, your ear is the best tool u have, I heard it and knew immediaty what it was! works for me a touch lean at the truck and spot on for the play area, done deal, unless it gets a touch colder, one main jet size should do the trick. agree with CASTLEDMAN
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