How Do I Read My Plug?

[PHIL_B54]

Feb 8th is the day(I hope) i just bought an WB R4 slip on , k&n/outerware , edelbrock Qwicksilver, and im waiting foreverything to arrive, the stock header welds will be ground, and 3-4 spark plugs on hand
I thought there was something in the frequently ask ? section but i cant find it. i did find this
http://www.trinityracing.com/techtips/index.html#10

am i going in the right direction? what else do i need to know.

thank you for the help
and
thanks everyone who helped with my pipe choice

[JOEX]

Looks like there is some good info there. I noticed that most of the Q's are based towards 2-stroke motors.

Anyone know if there is a difference in plug readings from a 2-stroke and 4-stroke?

Joe

[Loeryder]

2 stroke plug reading (http://www.eric-gorr.com/techarticles/sparkplugs.html)

4 stroke plug reading (http://www.motocross.com/motoprof/moto/mcycle/plug2/plug2.htm)

Not sure how big of a difference there is in method, but with 2 stroke you have to expect some oil to be burnt on the plug.

[cals400ex]

with the 4 stroke you want the tip of the plug to be a light tan color. a white color will indicate a lean setting and black with carbon build up will indicate a rich setting. you have to remember that there is pilot and main jets. there is also a needle with clips. main jets are for full throttle performance. the pilot jet is for starting and 1/4 throttle or less. the needle is for 3/4 to 1/4 throttle. a properly jetted carb will make your bike run better. i just have a stock 400ex with airbox mods and i jet it with temp changes and i have been known to beat 400ex with pipes and filters just because their jetting is wrong. they are all wondering "what the ****" when this happens. as far as performance goes, make sure your valves are adjusted frequently also. i picked up speed after i adjusted them. i did not realize how important this was.

[PHIL_B54]

my edelbrock carb has no clip to adjust, just the dial
i hope it will be pretty easy, i dont know where to start
13, 15 ,or 17 needle, im thinking ill start on the 15 i need to research more but i know i start 14-16 clicks from full rich then adjust accordingly

what about a plug run? dont i have to tun at high rpm for a while then kill it or something, before i read the plug?

thank you guys

[SmokinJoe@PJR]

Warm up the machine,ride at moderate pace for a bit. You will need to find a long straight to run flat out in high gear.At the fastest part of your run ,pull in the clutch and shut down the motor. Pull the plug out as soon as you can(Darn thing will be hot!!!!)READ THE PART OF THE CERAMIC DOWN IN THE BOTTOM.This is where you get the truest reading of the plug. The collor will be differant than up by the electrode.

[AndrewRRR]

What I've always been told (by some really good race engine builders) is you need to look at the "smoke ring" on the plug, not the tip. Up the ceramic electrode shielding, under the metal threaded part that you screw into the head, there is a dark (or tan, or light) colored ring. That's what you read. They have lights you can get to look up into the plug, on the ceramic part that is under the threaded metal shield (you can also cut the threaded part off with a hacksaw to check it out, but that is a lot of work for a plug reading.
If it's really lean you'll know. Once on the racecar after changing to headers with huge primaries we had gray plugs...with specs of burnt aluminum (piston) on them :eek: Had to go up 2 jet sizes on the holley dominator (a lot on those carbs).

[AndrewRRR]

Also, make sure you use a fresh plug (so you get an accurate reading), and I'd actually wait for the motor to cool down a little bit. The plug color won't change. If you pull it off while it's still hot, you can stretch out, or damage the spark plug boot.
If you ride MX, do your plug chop in 5th gear, if you ride dunes do it in 6th. Just ride around for a little bit to get a bit of color then do your chop (otherwise it might be too light to see). Then run up through the gears WFO, when you are tapped in 5th or 6th pull the clutch and hit the kill switch at the same time (pull the clutch so the motor won't keep spinning). Pull the plug and read it.

[Steve-o 400EX]

Originally posted by Loeryder
2 stroke plug reading (http://www.eric-gorr.com/techarticles/sparkplugs.html)

4 stroke plug reading (http://www.motocross.com/motoprof/moto/mcycle/plug2/plug2.htm)

Not sure how big of a difference there is in method, but with 2 stroke you have to expect some oil to be burnt on the plug.

Great links Leo.:cool:

[250x#93]

So whats it mean if a plug is half white and half black?

[Steve-o 400EX]

Click on the 4 stroke link and it will tell you!:rolleyes:

[PHIL_B54]

i had heard to do the plug run in 3rd or 4th
i guess im set then
good info guy thanks for the help:D

[AndrewRRR]

3rd or 4th might work as a good idea of where your jetting is if you don't have enough room to do higher gear plug chops. In 6th wide open your motor will be under maximum load. Some of the "supertuners" that we have worked with are good enough they can tell how your jetting is (pilot, needle, main) just by listening to it (or smelling it or looking at the exhaust) when you fire it up and drive it up onto the dyno! neat

[luvmyex]

easy just look at the #'s and letters on the side of it:D