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Plug reading 101

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Posted by: imlostagain

Ok , I have run into a problem with jetting my CR 144. I just installed a 1368 needle( Mr.Gorr's reccommendation) and reset my V-Force reed tension to the low setting .My problem is that I do not have a main jet large enough to get a good plug reading.I currently have a 180 main installed and the bike runs excellent through the whole range. I can ride aggressively for like 20 minutes and pull the plug it looks perfectly tan but not when doing a WOT plug chop(plug will be white ) I plan on going to a local race in the morning and am wondering if I can get away with running a richer ratio like 40:1 (currently 36:1). Would I risk engine damage ? Or will that even be enough to make a differance??If I recall Eric Gorr had suggested going to a 162-165 main so why Am I needing to go so large on the main Thanks again for ANY help on such a short notice.....


Posted by: crkid

first, going from 36:1 to 40:1 would be running leaner, not richer. i take it you're racing MX, so you will be at high rpms much of the time. running it leaner would not be good for the engine. going to say 32:1 ratio may not make a difference, except the plug may foul sooner. but if you are a person that keeps the bike revved out, then that could be your best bet until you can really get in and tinker with it. sorry for poor info, but it's the best i can do with what i got.


Posted by: Rich Rohrich

Quote:
Originally posted by crkid
first, going from 36:1 to 40:1 would be running leaner, not richer.


Changing the ratio from 36:1 to 40:1 would put more fuel into the chamber, but regardless it's unlikely to help the situation.

Within the framework of the limited info you provided it sounds like the plug you are running may be a bit warm for WOT operation on your setup, or you aren't reading the plug in the correct area. Remember you can't read the main jet from the nose of the sparkplug insulator.


Posted by: imlostagain

I have been using a NGK BR9EG .Should I try the BR10EG?
I may not have access to the "EG" plugs in the morning but should be able to get the "ES" . Might that suffice for the day. Thanks .....


Posted by: Rich Rohrich

Quote:
Originally posted by imlostagain
I have been using a NGK BR9EG .Should I try the BR10EG?


NO, if you are running a 9 then the plug heat range is not the issue. Reading plugs isn't a simple task so if your bike runs strong at WOT and it isn't knocking or pinging or overheating. Then fill up the tank and ride it.


Posted by: imlostagain

As for reading the plug...... I believe I understand where to look ( inside the plug on the ceramic)and the plug does show a nice tan color under general riding. To be honest I'm not entirely certain what a lean plug looks like . I am under the impression it is lean simply due to absence of coloring on the insulator but the electrode is clearly white during a WOT plug chop in 5th gear for 20-30 seconds . The motor was warmed up and I was riding in a slightly inclined field. Am I correct??


Posted by: Rich Rohrich

See the black ring at the bottom of the ceramic? That's where you have to look to read the mainjet. All you are reading higher up is the plug temperature. In the case of the pictured plug the heat range is a little too cold and could probabaly go up a step on the heat range and the mainjet is pretty close to perfect. It could go a step leaner on the mainjet without any problems.


Posted by: imlostagain

OK Rich, Upon further inspection the plug does have a "slight" tan coloration further down into the plug. Can I assume the 20-30 second ride wasn't enough to get more than a "slight" tan or should I try another size richer? Is there reason for concern with the white on the electrode after a WOT plug chop ? Thanks for the great example.....All this time I was looking about a 1/4 of the way into the plug. Would the fact that my insulator is tan after a day of riding indicate the overall jetting is relatively close or does it primarily diagnose 3/4 and up throttle positions?


Posted by: Rich Rohrich

Quote:
Originally posted by imlostagain
.....All this time I was looking about a 1/4 of the way into the plug. Would the fact that my insulator is tan after a day of riding indicate the overall jetting is relatively close or does it primarily diagnose 3/4 and up throttle positions?


That portion of the plug doesn't tell you anything about the mainjet or anything else about the jetting other than how the current jetting influences the relative plug temperature.

If you can't see down to the ring at the base of the insulator (see the picture) then you aren't reading anything relevant in terms of the mainjet strength PERIOD. You can't "read" the pilot or needle setting on the plug regardless of what people tell you, so don't waste your time.

Running the engine WOT for 20 to 30 seconds under a load (like sligthly uphill) should be enough time to produce the mixture ring at the base of the insulator but whether or not it will produce noticeable color at the nose (top) of the insulator will depend on the oil type, oil volume and the fuel you are running.


Posted by: Jaybird

imlost, use a flashlight to look down at the base of the insulator. Almost impossible to do in regular light...or without a nice lathe.


Posted by: Rich Rohrich

I guess I should have made this clearer. Jaybird is right, you can't see the fuel ring with the naked eye when the shell is still attached to the plug. You need a light and some kind of magnifier to see down in there where the metal plug shell and the insulator meet.

The standard Champion plug viewer looks like the picture below, Childs & Albert sells a newer style viewer with two lenses 5X and 10X. I have both and the newer C&A version is far superior. It costs about $65 but that's cheap in the long run


Posted by: bscottr

Rich,
Excellent thread. This one should be renamed "How to read a plug.....properly!"

Thanks,
Scott


Posted by: Rich Rohrich

As long as we've started down this torturous road once again we might as well do it right and take the discussion to the next level.

It's important to understand the significance of the rider, the track, the fuel etc when attempting to read a plug. The same engine with the same jetting can have plugs that look radically different when you change the load or the amount of heat going through the plug. This is one of those areas where explaining it doesn't provide enough information so showing clear pictures hopefully will help further everyone's understanding of the subject. Below are four pictures of plugs 2 pictures as complete plugs and the same plugs with the shell removed. These were pulled from my 2001 CR125 at DW01. One plug was a BR8ES one was a BR9EVX.

I won't tell you anything more till later. Draw your own conclusions.
Take a look at the pictures and think hard about what you are seeing. We'll pick up the discussion after you guys get a chance to check out the pics. Have fun.


We'll start with the BR9EVX with the shell removed.


Posted by: Rich Rohrich

BR9EVX with the shell


Posted by: Rich Rohrich

BR8ES with the shell removed.


Posted by: Rich Rohrich

BR8ES with the shell


Posted by: Rich Rohrich

another view of the BR9EVX


Posted by: Rich Rohrich

and another view of the BR8ES


Posted by: SFO

Are you running the same fuel in all of these plug pictures?


Posted by: Rich Rohrich

Quote:
Originally posted by SFO
Are you running the same fuel in all of these plug pictures?


Same fuel & oil.

Don't let the yellow tint on the BR9EVX shell pics confuse you. The actual color is closer to white (see the cutaway shot) , it's just hard to white balance this type of shot and still show the correct details on the threads and the flat of the shell.


Posted by: SFO

So what was you fuel blend for this bad boy?
MTBE cocktail ratio in what base fuel?


Posted by: Rich Rohrich

Fuel was Phillips B35 with some additional MTBE
Oil was Phillips Xamax mixed at 18:1


Posted by: SFO

that kinda kills my lead deposit theory...
Is the nose projection the same with both plugs?


Posted by: Rich Rohrich

Quote:
Originally posted by SFO
Is the nose projection the same with both plugs?


Yep, it's the same.


Posted by: SFO

It almost looks like an ignition timing change, just fishing...?
(I'm hooked)


Posted by: marcusgunby

I dont like the look of the 8 plug-looks like piston fragments.


Posted by: imlostagain

Rich , I would just like to say "Thank You" for spending your time educating us . I've come to realize that this is FAR more complex than I was aware of. I look forward to the remainder of this thread. As far as your plugs....I'm guessing the BR8ES was a little too hot a plug and caused a little flaking of the piston and blistering of the plug...Maybe??? Rich, How are you removing the shell from the plugs anyway?


Posted by: Rich Rohrich

Quote:
Originally posted by marcusgunby
I dont like the look of the 8 plug-looks like piston fragments.


The little metal bits/fragments you see are from cutting the plug shell off on the lathe. I should have blown them off with compressed air first. The rest is just normal carbon and flaky deposits that didn't burn off.


Posted by: jmics19067

can I take a guess?

the b9 plug is a colder plug but burnt cleaner at thetip yet looks a tad bit richer on the bottom . My guess is that the b9 plug was used in either a motocross or desert type run in the middle of the day and the b8 plug was used in a enduro /trail riding run in the morning when the weather was cooler.

Knowing that it was the same bike and the same fuel and assuming same rider and same day. Just taking a guess in the quest of knowledge and ready for all criticisms. And waiting for the real answer!!!!!


Posted by: bscottr

Quote:
Originally posted by Rich Rohrich
It's important to understand the significance of the rider, the track, the fuel etc when attempting to read a plug.


Rich, er, Professor Rich ,
I want to make sure I'm with you. Of the above we know the fuel hasn't changed, the bike has the same jetting for both plugs and the metal flaking has no consequence. A few questions:

Same rider? Slower rider, richer condition due to lower RPMs, hence the need for hotter plug.

Significant weather changes? Cooler in the A.M. = BR9. Warms up in mid day and/or rains (humidity) , richer = BR8.

Track changes? Dry, fast and on the pipe, BR9. Possible rain, wet and slow = BR8. Or (partly agree with jmics) BR9 = mx, BR8 = trails.

Any combination of the above?

Quote:
Originally posted by Rich Rohrich
The same engine with the same jetting can have plugs that look radically different when you change the load or the amount of heat going through the plug.


I understand this statement, at least I think I do . Could it be that the jetting was good for the differing heat ranges?

This is good and thanks for taking the time to do it. One other question of interest while we're here, no bearing on the above. Resistor or Non-resistor in modern bikes?

Scott


Posted by: MikeT

This is gettting very interesting. I am in the same boat and am trying to read my plugs from this past weekends ride. I'll admit I was looking at the tip and not the base like Rich as pointed out. When I get home, I'll shine a light down in it and attempt to get a better look deeper into it.


Posted by: Rich Rohrich

It's a trick question of sorts that will hopefully illustrate a point about plug reading and tuning in general.

Both plugs are from the same track, same fuel, same oil, same atmospheric conditions (within 70ft altitude density), but different riders. The BR9EVX has 30-40 FAST laps on it with Jeremy Wilkey twisting the throttle. Jeremy is one fast MoFo on a 125 and can keep the throttle pinned for a good portion of the track at Casey. The BR8ES has about 12 laps on it with me riding. I'm not a fast anything on a 125 so a lot less heat is generated in the engine so the plug temps are a LOT cooler I tended to short shift with this engine because Eric and I built it with a TON of compression and really small transfers so it has lots of low end for a 125.

The points in all this:

- If you look closely you'll see that the fuel mixture ring at the bottom of the insulator is virtually identical as well as the ground strap and the flat portion of the shell where the ground strap is attached (within the confines of the different plug bodies). The plug INSULATORS look dramatically different but the jetting is pretty much spot-on in both cases.

- Even though Jeremy rode the bike with a colder plug he generated enough heat to keep the insulator at the proper temperature and it burned off the deposits AS IT SHOULD. Looking at the nose of the insulator most people would freak out because it was clean and tending towards a whitish/light tan color and slow the bike down by bumping the main up till the plug cooled to the point where it wouldn't burn off the deposits and it would show some brown color that would make them sleep better at night. They have a name for those people, the guys with SLOW bikes There is enough of a fuel ring that the engine could have been run with a step leaner main and still been perfectly safe even with Jeremy riding it. If he had been racing it that's what I would have done.

- Even though I rode the bike with a full step hotter plug (BR8ES) I just don't ride it hard enough to generate the type of heat to keep the plug clean. Most people would have looked at the nose of the plug and thought the bike really running rich. If I had been riding with the 9 in the bike it would have been really covered with deposits and the lookey Lou tuners would have believed it was hopelessly rich. It's possible that I could have run a BR7ES but Casey is a pretty fast track in places so it wasn't worth the risk for me. A projected nose BR8 would likely have helped keep the plug a bit cleaner with me riding it. Regardless of how fast most people think they are they probably are running a plug that is too cold for their bikes. Jeremy is a really talented rider and a natural on a 125.

The moral of our story? Plug temperature is a critical factor if you ever hope to tune sharp, and reading plugs takes a lot more work than looking at it from 3 feet away. You have to understand the effects of your fuel, your oil, the track and the rider before reading plugs will be useful. It's worth the effort but I can tell you after peering at plugs for 30 or so years I still have more questions than answers most days. :D


Posted by: bscottr

Rich,
Does the size of the fuel ring vary with rich/lean condition, or is it only the color? Do you have a cut away pic of a lean plug?

Love tools so I gotta have a plug viewer now. What a spode looking at my plugs with the naked eye!

Resistor or Non-resistor in modern bikes?

Thanks,
Scott


Posted by: Rich Rohrich

Quote:
Originally posted by bscottr
Rich,
Does the size of the fuel ring vary with rich/lean condition,


Absolutely. As the jetting gets leaner the ring gets closer and closer to the bottom of the insulator. Once it disappears you can get into trouble pretty quickly. It's pretty dangerous to let the ring get too small on a two-stroke.

I'll dig around here and see if I can dig up an excessively lean plug.

As to your earlier question, I consider it pretty foolish to save a few cents on non-resistor plugs and put you CDI at risk. Of course that won't keep the cheapskates of the world from using them anyway.


Posted by: bscottr

Rich,
I always looked for color prior to this thread. Thanks for the education. 3 credit course?

IRT the resistor/non-resistor question: I've always leaned in the "R" direction for that reason. In a recent thread I brought up the issue and wanted to verify my bias. Here's the link:

http://www.dirtrider.net/forums3/sh...?threadid=46763

Thanks Again,
Scott


Posted by: Rich Rohrich

Quote:
Originally posted by bscottr
Rich,
I always looked for color prior to this thread


The color of the insulator is still very important but I think the trick is to look at it in the correct context.


Posted by: SFO

Rich, clean out your pm's and check your ucm account.


Posted by: jmics19067

thanks for the test <trick question> and the knowledge Mr.Rohrich. I for one am going to put this knowledge to good use . Let me know whenever you are going to have another schooling session because I want to sign up for the class!


Posted by: MikeT

So, Rich, what you are saying is that we can't really read the fuel ring without one of those tools, correct?

Second question. While riding on Sat, we put the BR8 in and the insulator was white so we switched to a BR9. When we pulled the BR9, we noticed that the insulator had a small spot of gray coloring on ine side of the insulator. What was the gray from?? (Amoco 93, SuperM 32:1)


Posted by: Rich Rohrich

Quote:
Originally posted by MikeT
So, Rich, what you are saying is that we can't really read the fuel ring without one of those tools, correct?


Unless you want to cut the plug open the plug viewer is still the best way to get consistent results.

Quote:
Originally posted by MikeT

Second question. While riding on Sat, we put the BR8 in and the insulator was white so we switched to a BR9. When we pulled the BR9, we noticed that the insulator had a small spot of gray coloring on ine side of the insulator. What was the gray from?? (Amoco 93, SuperM 32:1)


Hard to say. It could be junk in the fuel, it could be aluminum from the combustion chamber, it could be just an odd colored splash deposit.


Posted by: pontiac

Quote:
Originally posted by Rich Rohrich
...It costs about $65 but that's cheap in the long run


Rich,

I'm not sure if this is the same as the Childs & Albert spark plug viewer that's been repackaged, but here's one for less than $30 that looks very similar. I had a spark plug viewer from Comp Cams a while back before my kids lost it, but I've also seen them from Tavia, Moroso, Champion, etc.

http://www.speedwaymotors.com/produ...7UD96T6C7WX104B


Posted by: Rich Rohrich

That viewer is similar to the Champion version. They work well but they just don't seem to hold up as well. The CA version I'm using looks like the picture below.


Posted by: pontiac

Quote:
Originally posted by Rich Rohrich
...The CA version I'm using looks like the picture below.


Ahhh...Thanks for the great pic! Now I know what to look for when I buy my next one, but this time my kids won't be playing with it - hopefully.


Posted by: Jaybird

Rich,
I noticed on the BR9 shot, there is a small burnt spot on the top/side of the insulator. I always have a burn spot on any plug used on my 125sx. On the boys yz125 there is never such a spot.
I attribute this spot to turbulence during combustion. Am I correct in assuming that this is a normal thing with some port set-ups?


Posted by: Rich Rohrich

Quote:
Originally posted by Jaybird
Rich,
I noticed on the BR9 shot, there is a small burnt spot on the top/side of the insulator. I always have a burn spot on any plug used on my 125sx.


That's just a portion of the plug that ran a bit cooler so it colors the insulator a bit more. I didn't make notes on the indexing of the plug but I'll hazard a guess and say that portion of the plug was probably facing back towards the rear of the bike (intake side) so it was the first part of the plug to see the loop of each fresh charge allowing it to run a bit cooler.

Different cylinders will show this in different ways.


Posted by: BRush

Quote:
Originally posted by Rich Rohrich
The plug INSULATORS look dramatically different but the jetting is pretty much spot-on in both cases.



Rich,

Great thread. This may be in the dumb question category, but the mixture ring in the photo seems pretty dark - yet you've described it as spot-on. Is this a photo color balance thing, or do I need to recalibrate my mental image of good plug color? A picture really is worth a thousand words with this stuff. If you do happen to find some good examples, it would be great to see a couple of photos showing a too-lean and too-rich mixture ring.


Quote:
Originally posted by Rich Rohrich
It's possible that I could have run a BR7ES but Casey is a pretty fast track in places so it wasn't worth the risk for me.


Is the risk in that case one of pre-ignition?

.


Posted by: yz_387

I think I have learned some important things here. I noticed that the spark plug on my 2002 yz250 still looked white (at the insulator tip) after over an hour of riding. Although the bike was running well, I was concerned that the mixture was too lean, so I put in a richer main. The tip then looked to be a whiteish-tan color. I thought that it looked better but perhaps still a little lean. After reading this thread I cut the plug apart, and was suprised by what I found. a very thick black band further down the insulator. I guess this means it is horribly rich? Should I lean it out until the thickness of the dark band matches that of the plugs in the other pictures in this thread despite the fact that the nose of the insulator is white? Thanks

http://www.dirtrider.net/TeamDRN/da...arkplugtip3.jpg


Posted by: MikeT

Quote:
Originally posted by yz_387
I guess this means it is horribly rich? Should I lean it out until the thickness of the dark band matches that of the plugs in the other pictures in this thread despite the fact that the nose of the insulator is white?
Wow, This is an EXCELLENT question and a great thread. I can't wait to see what Rich says about this. Good pic of the plug yz.


Posted by: Jaybird

I think about a 1mm ring at the bottom of the insulator is about right. The picture is about 5-6 mm's, yes? (way fat)

I agree, nice pic.


Posted by: Rich Rohrich

It looks pretty rich to me but unless you got this color from just a WOT throttle run there is no telling which of the circuits is too rich.

To answer a previous question. The color of the ring is less relevant than the size. Carbon is black and the ring is composed of carbon, so once there is enough of a buildup the ring will tend to be black as well. It's possible to read more into the color of the ring but you'll find it's very specific to the fuel and oil being run, so it can be pretty difficult to apply generalized rules to the ring color.


Posted by: yz_387

so the carbon band thickness is a result of all of the jets? I thought you said that this was how you determine the condition of the main jet.


Posted by: Rich Rohrich

Quote:
Originally posted by yz_387
so the carbon band thickness is a result of all of the jets? I thought you said that this was how you determine the condition of the main jet.


It is how you read the mainjet, but if you are riding around at 1/3 throttle opening with a needle that is too rich and the engine never sees WOT then the reading you get will only be for the circuit it's running on. Carbon collects when the combustion is incomplete regardless of the circuit. The ring is used to read the mainjet because WOT is the only time you can be sure you are getting the same reading (i.e. throttle opening) on the plug. Given the tapers of needles there is no consistent way to read 1/4 1/2 or 3/4 throttle on the insulator base.


Posted by: yz_387

Rich, thanks for the education in spark plug reading I know I have learned a lot.


Posted by: MikeT

Now all I have to do is buy one of those plug viewers or get a new Hack saw balde.


Posted by: Jaybird

Mike,
MSC Supply has a decent viewer. It is smaller than the premium models that Rich has, but works well.
www.mscdirect.com
10x Illuminated Coddington Magnifier (Bausch & Lomb)
#PN06546840 on sale now for $24.99


Posted by: Rich Rohrich

Quote:
Originally posted by Jaybird
Mike,
MSC Supply has a decent viewer. It is smaller than the premium models that Rich has, but works well.


I have one of those as well. They are useful for looking at the ground strap and the nose of the insulator but they won't allow you to get a good look down to the base of the insulator. Save yourself some money and buy the correct tool from the outset. :D


Posted by: dave186

Ive learned a lot from this thread, so I decided to sacrifice a BR8ES for the sake of jetting and this is what it looked like. One question I have, how long does it take to get the ring built up? I cut this plug open after about 2 hours of hard riding. http://www.dirtrider.net/TeamDRN/data/26367plug1.jpg


Posted by: Rich Rohrich

You can usually see a fairly distinctive ring in a single hard pass down the drag strip (9-10 seconds of running). A couple of minutes of hard running will give you a pretty good idea of what's going on.


Posted by: whyz

So would Dave's plug be too rich also?


Posted by: MikeT

If your jetting is spot on. Will the ring "grow" over time or stay the same size. Also if the bike is a little rich like yz387's plug, will the ring continue to grow until the tip is covered in black?


Posted by: Rich Rohrich

Once you have enough time to get a good reading if the conditions stay the same the ring will tend to stay the same. The problem is most people tend to ride at something other than WOT and weather has a way of changing over time so the conditions rarely stay the same for very long.


Posted by: Jaybird

Then one can assume that those who practice "predictive jetting", (taking into account all known variables and jetting by chart as a result of measurables) are a step ahead of the game and can, in fact, keep that lil bugger close to the same size, yes?

:confused:


Posted by: Rich Rohrich

Quote:
Originally posted by Jaybird
Then one can assume that those who practice "predictive jetting", (taking into account all known variables and jetting by chart as a result of measurables) are a step ahead of the game and can, in fact, keep that lil bugger close to the same size, yes?


I've never seen a "generic" chart that works for all situations or even particularly well in general, but over time good note taking and regular measurement of known variables will allow you to build a bike specific chart of your own. Once you have a baseline and have an understanding of how atmospheric changes impact those baseline settings you should be able to easily make changes without ever pulling a plug.

You'll almost never see Eric Gorr pull a plug on one of his rider's bikes. That's not a coincidence.


Posted by: whyz

Good questions Mike.


Posted by: Rich Rohrich

Quote:
Originally posted by whyz
So would Dave's plug be too rich also?


That would depend a lot on what type of riding he is doing.


Posted by: Kaw_Boy_5

If this is the correct way to read for the main jet what is the correct way for the other circuits? I was going on the assumtion that running at 1/4 throttle for a bit and the checking the plug was good for a pilot test but you seem to say it is not. Thanks


Posted by: Rich Rohrich

Quote:
Originally posted by Kaw_Boy_5
If this is the correct way to read for the main jet what is the correct way for the other circuits?


By feel or with a wideband oxygen sensor connected to a data acquisition system that also reads throttle position.


Posted by: Jaybird

As always, you are most enlightening, Mr.
Thank you.


Posted by: Rich Rohrich

Quote:
Originally posted by Jaybird
Mr.


Mister™ is a registered trademark of billywho™. All rights reserved. Portions ©2002, billywho™. Unauthorized use is a no-no.

Careful Jaybird or BillyWho will send the black helicopters to pay you a visit :scream:


Posted by: Jaybird

I think he's got his infringement lawyers looking at it now. I only used said term once before and it was immediately noticed.
I agree, a man needs to be careful!


Posted by: whyz

Thanks for a very good start of my day.
You guys are way too funny


Posted by: whyz

So with Dave's plug..
Do you think that ridin trails and MX,that this plug would be too rich?,
And can you tell by the look of the plug what type of riding the plug was being introduced to?? (just an opinion please) :silly:

Thank You.



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