In progress jetting question

[JCW]

Re: 03 KDX 200 w/ -35 pipe, stock gearing / 150 miles from the gulf coast at 500 feet elevation

I switched from a 160 main jet to a 152 and after a second WOT check, it was white hot. I went to a 155 (middle clip) and it looks very hot and dry, but has light-med brown porcelain on the inside around the plug gap after the WOT check. Both ways run very well and the transition from slow to fast is super smooth with the 152 and the 155 main.

I checked my 48 pilot jet and I could still get an RPM increase after 6 full turns out. Based on Canadian Dave's excellent carb tuning site, it appeared that I needed to drop down. I switched to a 45 and I can get an increase in RPMs up to 3 1/2 full turns out and then it seems to drop off. My concern here is that at idle, the plug looks just like it does after a WOT (super dry and light-med brown), anywhere from 1 1/2 to 3 turns out on the air screw.

The bike is running great, but I have a feeling it's a little lean, even though it should not be. One thing that does sound different is when I let off of the gas. It sounds like a "funny car" with a big cam. It has that "off the gas lopeing sound".

It may be perfect, but the always super dry hot looking med. brown color from idle to WOT makes me want to run this by the group and get an opinion.

Thanks for your help

JCW

 

[Tom Ludolff]

You could try 1 turn out on the a/s. It sounds like you're just about perfect though. As long as there is no hesitation going from idle to a quick half throttle, you're good to go. No need to be concerned about the plug appearance at idle. Just set the a/s and pilot jet for optimum throttle response.

 

[CaptainObvious]

Don't bother with a plug reading for the pilot circuit. Tune the bike for throttle response. Using the air screw as a measurement is the right way to go.

Looks like you have it nailed.

 

[wibby]

How are you reading the plug?

Color of the insulator means little, you need to remove the threaded portion from the plug and check the mixture ring. With a brand new plug after a WOT chop the plug will still look new and white, except for the ring, if one exists.

I think it would be safer to only drop one main jet size at a time. And first get the main jet dialed in before you start messing with the needle and the pilot (IMO)

6 turns on the AS? Lucky it did not fall out :eek:

 

[JCW]

Thanks everybody-

Wibby, don't worry I didn't let off pressure on the air screw because I was thinking the same thing. Regarding plug color, I was referring to the insulator on the inside of the plug when it is unscrewed. The metal (gapped) tip is always very dry and rust colored (?). My previous color references were to the porcelain around the (gapped) metal tip. I did a half throttle check today and it was identical to the idle and WOT checks.

What can you tell from the outside of the plug? I always checked on the inside where the mix is to see what was happening in the cylinder.

Today, I set the AS at 1 turn and it is now at least dark brown, but very dry on idle (still runs great and transition to mid to high RPMs is great). I'm thinking about trying a 158 main to be safe. I'm going on a couple of 200 mile dual sport rides soon (Kentucky LBL & Arkansas Ozarks) and I want to be sure I don't lock it up on a long ride. From all I've read, the 155 main should not be too lean, but it is very close if it is not too lean. This bike sounds like a "funny car" nitrous burner at 1/4-1/2 throttle (definitely cool, and hopefully safe).

Either way, it's better than before, has tons of power, and can take higher gearing with the extra power (maybe a 14 tooth countersprocket).

Thanks
JCW

 

[andrew]

While you blokes are dispensing great advice, I thought I'd get in with a question of my own.

My jetting is pretty close, I have great throttle response, EXCEPT after I havecoasted down a steep hill with the throttle closed - when I crack it at the bottom it bogs badly for a bit. I was thinking maybe my pilot is a bit rich, or maybe my needle is too high. I know a lot of folk run a 42 pilot but I use WOT a fair bit and I'm afraid of being too lean when I back off down a long hill.

BTW, I'm running a 155/45 with a CEL needle and the clip in the middle ('96 200)

Opinions??

Cheers,
Andrew

 

[G. Gearloose]

Andrew, your fat .. ;)
a CEL has quite a bit smaller dia. straight section than the stock needles, so a 45 pilot is too fat, more suited for the 1173,4.

Your pilot should be in the 38-42 range with the CEL.

Needle height won't help the symtom you desribe, and you can't hurt an engine under compression braking (unless you forget the oil)

 

[andrew]

OK, thanks GG, I'll try a 42 and see how it goes...

Cheers mate,
Andrew

 

[Houndog]

At almost sea level I am running a CEL-2 152/40. I did a plug chop to find the 152 ok but a bit on the rich side, waiting for a 148 and a 150. I tried to order 35 and 38 pilots locally but they can't get them.

My setup now is close, wheelies in 4th, loads up a bit but cleans out very quickly. With the stock needle it works pretty good mid clip with 155/42.

 

[wibby]

What can you tell from the outside of the plug?

Well you can tell what kinda plug it is ;)
But other than that I don't know where that question came from :think:

 

[CaptainObvious]

andrew, don't worry about too lean of a pilot and WOT operations. One does not effect the other.

 

[canyncarvr]

Repeated references to color make me wonder where the plug is being read.

Wibby said it already, 'With a brand new plug after a WOT chop the plug will still look new and white, except for the ring, if one exists,' ...but the response of, 'Regarding plug color, I was referring to the insulator on the inside of the plug when it is unscrewed,' doesn't follow to me.

'On the inside' when 'unscrewed'?

Check this to see what the mixture ring is supposed to look like. With a 10 second run on a new plug, the ring darkness isn't going to be nearly as dark as the pics that RR posted. It's probably not going to be any color, either.


The ground electrode is rust colored? Sounds like an octane booster has been added to your fuel to me.

re: when I crack it at the bottom it bogs badly for a bit.

Meaning it 4-strokes?

Yeah..your idle circuit is too rich. You shouldn't have that problem with a CEL with the correct pilot and AS adjustment....like gearloose said.

re: 'Either way, it's better than before, has tons of power...'

And that's the point of the whole thing, 'eh?

A little attention to carb tuning will benefit you hugely. Congratulations on having the ambition to expend some time getting it sorted out.

 

[JCW]

I'm becoming more and more convinced that I'm an idiot on this subject (OK, I hear the resounding applause). In all of the manuals I've looked at, it shows the bottom of the plug after it was unscrewed from the engine (where the gap is). If it's too rich it is wet and black, if it's too lean, the gapped tip is often partially melted off and the ceramic is white.

Canyncarvr, in looking at the picture you told me to look at, I am lost. That doesn't look like the outside or the inside of a BR8ES plug. The outside of the plug is where the plug wire snaps on and the inside is where the gap is (and where I was taking a reading and making a reference to the color). This photo has no gap although it looks like the inside of the plug). I apologize for my obvious ignorance and I hope you can stay patient until I get this right.

Thanks for your help and I will wear my dunce cap for a week.

JCW

 

[Houndog]

To look at my plugs inside I put them in a drillpress and hold a hacksaw against it, After I figure it has been there long enough I put it in a vice and use a pipe wrench to turn the threads 'off'. There are special lights/lenses to look at the plugs which lets you keep the plug intact for future use, but I 'snap' the ends off, write the jetting info on them and store them for my reference.

Canyncarvr, do the first couple of letters of BR8ES stand for Bel Ray?? Might be a sign :)

 

[canyncarvr]

JCW:
As you might infer from houndog's post, the pics on the thread I linked show a plug that has had the threads removed.

The ground electrode, being attached to those threads is also gone.

What you see is the bottom of the insulator that is normally (on a not cut plug) fairly well obscured by the parts removed in the pics.

As HD mentions, there are tools that are available that provide light and magnification for the purpose of peering down into the recesses of the plug...but it's hard to see what's going on even under the best of circumstances with the thread ring attached.

Hence, it is removed.

re: If it's too rich it is wet and black, if it's too lean, the gapped tip is often partially melted off and the ceramic is white.

If you are running too rich, your plug will likely be wet and black, but that's not how you tell what your air/fuel mixture is.

If the gapped tip is melted off, you have more problems that too lean. You may well BE too lean, but again..that's not how you tell what it is you want to know......what your air fuel mixture is.

You're looking for a darkened ring at the base of the insulator that is optimally about 1mm wide. The longer the engine is operated under WOT conditions, the darker the ring will be. Any color at the tip is not indicative of air fuel mixture. Plug temperature and fuel deposits contribute largely to that 'color'.

Don Ward, Motorsports Engineer for Autolite:

“When you tune the engine correctly, on the base of the tip of the porcelain it will look like you've taken a pencil and drawn a real light ring around the tip. That's what you're looking for when the engine is tuned correctly. If you've got too much fuel it will be a real wide ring, and if there's not enough fuel there won't be any ring in there at all -- the insulator will be completely clean."

Note he interchanges 'base of the tip' and '..ring around the tip.'

In both cases he is indeed referring to the base of the tip.....having nothing to do with where the 'bendy thing' is (ground electrode welded to the thread ring).

How's that?

Crystal clear I'm sure.

Oh no! Belray plugs!!??? :(

 

[JCW]

Thanks for the explanation and sorry for taking up so much time on this one.

I obviously went to Belray Technical School-

JCW

 

[canyncarvr]

Just checking.....but that explanation cleared up your questions? Clear? ...or clear as mud?

If you have a question, ask. If I have an answer, can find an answer, refer you to an answer (or can make up something without too much trouble), I will.

 

[JCW]

Thanks a lot for helping. I understand what you are saying. I tried to get the spark plug apart last night, but had no luck. I will probably just take it in and get the mechanic who has worked on my bikes for years to jet it. I went back up to a 155 @ the middle clip, 45 @ 1 1/2 turns on AS and I think it's really good. My big concern is being sure it is not too lean. As I mentioned earlier I've got a 2 +200 mile cross country rides coming up and I don't want to sieze a piston in the middle of the Ozarks. I looked inside the plug with a flashlight and magnifying glass and it is light-med brown as far as I can see, but I can't see the base of the porcelain to check for a dark ring.

Thanks again,

JCW

 

[canyncarvr]

Nah! You don't want to do that (take it to someone else). He/she/they/it can't jet it to fit you...you have to jet it fit yourself.

Besides, the knowledge and experience you gain will be very important to you at later dates. You can't be taking it to the shop every time you change riding areas, elevations...change your riding style (with experience) and/or the temperature drops 30º.

Besides THAT, I haven't taken a single piece of hardware or machinery to someone else to be fixed that didn't get messed up somehow. Trust yourself and your learning ability. You will be much better off in the future.

Cheers!

AND...you're welcome! ;)

 

[JCW]

Thanks, I will put in a new plug, do a WOT check tomorrow and cut it open with a hacksaw, since I can't figure out how or where to open the plug. Right now, it is 100% better and has a lot more power. I'm very pleased with it and I think it's right where it needs to be. It cranks easy, idles well, and rips in any gear from idle to WOT. After this, I may go up to a 14 tooth countersprocket for cross country riding and switch back to the 13 for hills and technical stuff. That's an easy and fast way to adjust gearing (although I will have to file or remove the chain guide on the front). After all of this work, I've acquired a small arsenol of pilot and main jets for trips and temperature changes.

Thanks,
JCW

 

[canyncarvr]

re: I can't figure out how or where to open the plug.

Sure you can.

'..cut it open with a hacksaw...'

You just did! ;)

Have fun!!

 

[JasonWho]

---

 

[Jackpiner57]

You can use a pneumatic die grinder with a whizzer disc on it to cut the threaded portion off of the plug(cut it at the base of the ceramic insulator). If you don't have one of those, any auto body shop can do it for you. Just put the nut part of the plug in a vise and cut where indicated. Wear your safety glasses!

 

[JCW]

I put in a new plug today and rode for about 10 minutes to warm the bike up. As the bike is so strong for the stock gearing now and I did not have a hill or anything to put a load on it, I ran it close to wide open for 10-15 seconds and did a WOT plug check (it was screaming like it would explode at any minute in "free reving" style, 5th gear). I know, time for a gearing change also.

I will bring home a digital camera from my office and get a picture, but it's real easy to explain. I cut the threads off and the top porcelain area (where the tip is on one end and the mixture ring is on the other end) was totally white everywhere except for the mixture ring. I have a dark brown mixture ring that is about 1 1/2-2mm thick. Again the rest is totally white and the bottom porcelain portion below the mixture ring (going towards is the tip is totally white). It looks like a brand new plug except for the brown ring.

It runs awesome with no problems. Does this sound safe? The temperature was 90 degrees with high humidity (summer in the south!!!). I'm riding in Kentucky in a couple of weeks and it should be a little cooler, less humidity, and a little higher elevation. What should I be concerned about with those changes?


Final question. I went from a 48 to a 45 pilot jet and although I haven't cut the threads off, at 1 turn out on the AS it runs fine but the plug (with the threads on) has a very dry med. brown general appearance. With the AS 2 1/2 turns out, the plug is very dry and white to light tan in appearance. Should I do an idle test and cut the threads off again, or does this sound fine? Either way, it revs smooth and fast from idle to 1/2 or 1/2 throttle at either position on the AS.

Currently settings as if today's test:
155 main (at middle clip)
45 pilot 1 turn on AS
Air Box cover cut to 75% open
Stock gearing
FMF -35 gnarly woods pipe

Thanks everyone for helping. I hope the readings sound good, because this bike is starting to remind me of my last KX250. It is a blast to ride.


JCW

 

[G. Gearloose]

Originally posted by JCW
Should I do an idle test and cut the threads off again,...

Uh, no...

Unless your setting the main, don't look at the plug with the same scrutiny, nor should you care or use it to tune any other circuit other than to reassure qualitatively (I am indeed leaner/richer than before).

Everything but the main is set seat-of-the pants to suit your riding style/ability/terrain.

Set yout AS for best off-idle power and responsiveness only. (read UNDER LOAD)

Have you tried any needle clip position other than middle? Now that you have set the main, this is your next step to tune 1/2 throttle position.