spark plug

[tri-z_250R]

i just put this plug in yesterday and it seemed like it was running fine, i just dont know how to read it. i took my trike out riding foor about and hour or so yesterday to see how it was running (lean or rich) but i dont think i have ever seen this before.... one side of the insulator is black and the other side is a brownish tan color, and the tip of the plug that you cen bend to gap it is part black and a whitish color. i scrapped off the black on it and there was a hard chalky layer over the metal. also around the outside of the plug where the threads start it is all black around the edge. do you know what this means? what do i need to do to fix it? heres some pics

[hotroddal]

looks like your running pritty lean, its probly your jetting

[TeamGeek6]

First, realize that "its running fine" Thats the most important observation.

My spark plugs do the same thing, I call it the "hemisphere." (a clear dark/light line on the porcelain). On mine, its not black and white, but white and a faint brown.

The white areas are where the fuel is burned completely, the black ones are where it does not. Premix oil has something to do with it on 2 strokes. Notice the end of the spark plug shell will always be black because it runs very cold AND that it is on a "boundary" where if the A/F charge touches it, fuel will load up. That has less to do with air/fuel mixture than cylinder design.

The white and black areas will line up with areas in the cylidner away from cold spots like the head dome. The black or brown areas on the porcelain should fall as far up in the shell as possible to prevent fouling. If the brown or black areas reach the center electrode, the plug is fouled and may not fire right.

Put the plug back in and notice the "index." Index means the position of the spark plug gap with respect to the exhaust port. My 250R is indexed to 270* which means the spark plug gap is opened up to one of the intake transfer port (intake valve on a 4 stroke).

Once you find the index, remove the plug and hold it the same way above the head and look at how the colors line up with the cylinder.

A LOT TO LEARN HERE!!!! :naughty:

There is an entire SAE (Society of Automotive Engineers) paper devoted to this, to spark plug electrode design and orientation. If'n ye want, we can do a thread and learn a little about it.

Youre getting on the razor edge of engine tuning looking at things like this. If you watch top fuel racing and see the mechanics looking at spark plugs through a magnifying glass, this is what they are doing. :Bounce

PICTURES:

1.) Pictures of a 8 and a 5 heat range plug

2.) A 5-heat range spark plug from my ATC 250R, notice the dark brown ring is up the porcelain where it cant foul the gap. Notice the shell is clean, no black deposits on the shell, its all burning clean. During the tests this spark plug came from, the exhaust pipe (a few inches from the cylinder) would run at 180*F on full hot idle.

Also notice all the screaming and crying on bulletin boards about "you cant run a 5 heat range spark plug." :crazy: Do you see any damage on that spark plug? They all scream "Itll overheat!" Do you see any melted metal? he he he

3 ) A clip from the SAE report on spark plug gap design showing what a spark plug should look like

[md1985250r]

Thats some good info right there. :w00t: THANK YOU

[Hornetpowerspor]

It looks to me like your motor developed an intake leak. By the pics the insulator looks white. You want a cinnimon color when you do a plug chop. You may want to check your base gasket, or crank seal on the Ign side of the motor, carb boot, and head gasket for a leak. The easiest way to do this is start your trike up, and while idling spray some either around those places and listen for an increase or decrease in rpms. That will help you narrow down the issue. Also may look at the main and pilot jets in the carb and see that they aren't plugged.

[OldSchoolin86]

Put the plug back in and notice the "index." Index means the position of the spark plug gap with respect to the exhaust port. My 250R is indexed to 270* which means the spark plug gap is opened up to one of the intake transfer port (intake valve on a 4 stroke).

Once you find the index, remove the plug and hold it the same way above the head and look at how the colors line up with the cylinder.

A LOT TO LEARN HERE!!!! :naughty:


Indexing in a hemispherical combustion chamber (2-stroke) is a total waste of time. Indexing is more beneficial in 4-strokes and even in the best of race motors HP gains are 1% at best. Talk to any engine builder and you'll find out that unless you own a dyno and absolutely need that tiny edge it's not worth doing. The gains are so small that none of us would ever notice it. Also it is typical to index the plug to face the intake but in some cases indexing to the exhaust will yield more HP. This is why you need the dyno and a lot of time.

By the way, those plug pics are horrible tri-z_250R but from what I can see you're close.

[tri-z_250R]

By the way, those plug pics are horrible tri-z_250R but from what I can see you're close

yeah my camera is a cheap pile of crap. if i got any closer with the camera it wouldn't have showed up! thanks for the help.

[jenndnn3]

Here is a good artical, however, I was just really after the clear pictures in the middle of the artical itself. It shows some different scenerios with plugs. You can get a idea what is going on. If you do more searches via search engine, you will find tons and tons of info on plugs, with picts, and what is possibly going on, if anything.

http://www.jetav8r.com/Vision/Ignition/CDI.html

[TeamGeek6]

yeah my camera is a cheap pile of crap. if i got any closer with the camera it wouldn't have showed up! thanks for the help.

Thats what I used, the cheapest camera there is, but I took it apart and adjusted the focus and it would snap pictures real close.

Oldschool, I dont go by engine tuners opinion[/*], I study the engineers that design automobile engines. Go to www.sae.org, drop your opinions at teh door and learn something!

[OldSchoolin86]

Thats what I used, the cheapest camera there is, but I took it apart and adjusted the focus and it would snap pictures real close.

Oldschool, I dont go by engine tuners opinion[/*], I study the engineers that design automobile engines. Go to www.sae.org, drop your opinions at teh door and learn something!
http://www.3wheeler.org/vb/images/smilies/doh.gifI don't know why you like to act better then people but my "opinions" came from the good engineers at NGK and have been proven by "engine builders".

[bigyellow4x4]

heres my 2 cents , mine looked like that when i was rich on the bottom idle to .5 throttle but correct on wide open. you get the black on the out side and good burn on the center.
Was that checked at wide open? how old of plug older plug might look like that too (becouse never getting hot enought to burn outside clean?) Always use new plug and check .5 throttle and wide open, than if it feels good your very close or as close as you need to be lol!!