Topic: Plug Chop

[Wis]

Ok...so i did a plug chop. I know tan is good......and white is bad.(right?)
 So what's it mean if one side of the insulator is tan....and one side is white? is that normal?...if so, which do i go by....the tan or the white? the electrode(well the arm ) is tan.

[kettlesd]

Any chance you can post a pic of that plug? Without seeing it, it sounds like your borderline lean though.

[Wis]

ok...after looking again, i think you're right...i'm on the lean side...much more white than there is tan...but could that just be from having a heavy hand on the throttle? i'm workin on posting the pic.

[Wis]

yes, did the chop WOT...uphill. after looking at all 4 plugs...it seems like more of a tan spot, ass opposed to half/half. and how do i get my pic to post?

[Wis]

trying to post pic

[TwoTired]

 While some information can be retrieved from the electrodes, it is the center electrode insulator where you want to read the plug deposits for mixture conditions.
Compare yours with:
http://www.dansmc.com/Spark_Plugs/Spark_Plugs_catalog.html

From the pics you posted, the left plug is either new or lean as the insulator has no deposits.

Cheers,

[Wis]

Thanx for the link Two....should have said that those plugs are both in same condition...just showing the white side of one and the 'tan' side of the other

[TwoTired]

There are those that index the plug, (adjust the electrode position) to evenly distribute the combustion deposite and even up the flame travel.

Under what conditions was the plug chop for those plugs done?  What throttle position and load?

[Wis]

hey two....was wot...uphill...200#rider.....going by the link, i'm either photo 22 or 23. And WOW...i'm not a newbie anymore! cool!

[TwoTired]

I'd say your plug color is perfect then, provided you are at or near sea level, the barometric pressure was high, and low humidity.

You should have been making good power, as well.  If you were to spend most of your engine run time under those test conditions (like racing), I would consider using D8 plugs.  But, your main jet looks sized correctly, judging by those plugs.

Since you are nudging close to the too hot area, the things to be worried about, would be running at a lower altitude, or when a very high pressure weather system moves in, or both.

The plugs will hopefully darken a bit during throttle valve operation.

Nice work!

[Wis]

Well, now i got a swelled head...Two tired said Nice Work!( not meant sarcasticly). But i'm concerned about the humidity comment, as i'm in alabama....humidity here is gonna be around 90/95% in the heart of the summer. How will this affect things?...leaner or richer?

[TwoTired]

I guess I am stingy with compliments.  I blame an engineering bent for this.  Verbosity is generally only required when something is wrong.  If things are right, they are simply the way they should be.  Who needs to comment on the normal?

Here's how the fuel burn works:
The fuel draw we'll assume is more or less a constant.  So, the burn is related to how much oxygen there is in each gulp of air the cylinder takes.

High barometric pressure and low altitudes, compresses the air so more oxygen molecules are available to combine with the hydrocarbon molecules in the fuel.
Pressure increases with lower altitudes as there is more air stacked on top of it, causing compression.

Humidity in the air displaces oxygen, making less oxygen available in each gulp of air the engine makes.

So, the corner cases would be:
1) Low altitude, high baro pressure and low humidity= Most available oxygen per gulp of air.  S/b the leanest conditions
2) High altitude, low baro pressure and high humidity= Least available oxygen per gulp of air.  S/B the richest conditions.
If your plugs are on the raggedy edge of preignition, you want it to be under condition one, cause it won't burn any leaner than that with current jetting, and going richer won't destroy you engine.

Make sense?

[Wis]

Wow...i find it hard to beleive, but that actually does make sense!....i guess reading this forum everyday has done more than just improve my bike.....it's improved my mind!. Thanx again for all the help!
 Hope everyone has a fantastic weekend!

[Bob Wessner]

Here's a calculator that let's you play with temp, humidity and baro pressure to see the impacts on engine performance.

http://wahiduddin.net/calc/calc_hp_abs.htm