reepicheep

Member
Apr 3, 2009
670
2
My KDX-220 uses the stock NGK plug, $2.50 or whatever, rarely foul, life is good.

My son's KX-60 however uses a "race" NGK plug, that fouls all the time and costs $6 a pop. :(

If I decode the NGK product information, aside from the heat range difference (the KDX is an 8, the KX 60 is a 9), the other difference is that the KX plug is a fancy nickel alloy electrode.

NGK makes that exact same plug in a non nickel alloy electrode format (same heat range), for half the price.

So question 1 is the simple one... if my son was racing MX against Bubba Stewart and trying to pass him while jumping a triple, I'd want him to have gold plated nickel alloy spark plugs. And something other than a KX-60. :)

But we just ride around in the woods and play. So are there stealth reasons I can't use the non unobtanium plugs and just run the same style NGK's (with the proper heat range) that work so well on the KDX?

Second question... aside from the heat range, the plugs are the same. The KX is a NG9, the KDX is an NG8. So the heat difference is fairly minor. We ride together, so if we both ran the same plugs, I could carry a fewer different spares while we are out and buy them in bulk.

So if I switch the KX to the cooler plug, will I just have to jet accordingly, and maybe loose a little peak HP, and maybe warm up slower? If so, I would just run the same plugs in both bikes.

Any guru's with opinions? Thanks!
 

dirt bike dave

Sponsoring Member
May 3, 2000
5,349
3
For NGK, the higher the number, the colder the plug is.

So running an '8' in the 60 would be a hotter plug. I'd try that first, watching for signs it is too hot.

FWIW, for woods riding, I've run hotter plugs than Kawi specified with no ill effects, and no change in jetting, power or warm up. Just less fouling.

Kawi probably specs a cold plug for the 60 as it is a race bike and could be subjected to extreme conditions.
 

Matt90GT

Member
May 3, 2002
1,517
1
Changing heat ranges has always been misunderstood and kind of a myth of correcting fouling plugs.

"It is a common misconception that spark plugs create heat. They don't. A heat range refers to how much heat a spark plug is capable of removing from the combustion chamber."

Basically run to hot of a plug and overheat, to cold and carbon foul. If you are oil fouling, you need to adjust your jetting.

Best bet is to NOT change the heat range unless you know why to. Read up on plugs here:

http://www.ngksparkplugs.com/tech_support/spark_plugs/p2.asp?mode=nml

Now with that being said all my bikes run 9s and are jetted correctly. So no fouling issues. No overheating issues.

But going from a E to a G plug or IX plug will not change the heat range at all. Just the materials used. The IX plugs are awesome, dont gap them and are very resistant to fouling. Yes they are 9-11 bucks but worth it.
 

reepicheep

Member
Apr 3, 2009
670
2
Thanks all, great info!

Since I started the thread I figure I owe more facts here as I find them.

As per the NGK web site:
95-96 KDX-200: BR9ES
97-06 KDX-200: BR8ES
03-05 KDX-220: BR8ES
90-03 KX-60: BR9EG

"As a general guideline, among identical spark plug types, the difference in tip temperature from one heat range to the next is approximately 70°C to 100°C."

Lower numbers are hotter plugs (Thanks Dave!). So the KX is actually running a cooler plug than the KDX.

Target temp for the plug? Above 450 deg C and below 850 deg C (whoa! That is HOT).

charttempfiringend.gif


Oh the irony. My KDX is actually 95, so technically I should be running the same plugs as the KX-60, not the other way around. I wonder if Kawasaki just changed their mind, or if there are CDI differences?

Of course I now have the Eric Gorr 220 kit, so who knows how that changed it. If anything, I can probably run a hotter plug as the nicisil coating should do a great job transferring heat.

I couldn't find any details of the ramifications of the electrode material composition yet.

Cool info! Thanks all!
 

dirt bike dave

Sponsoring Member
May 3, 2000
5,349
3
FWIW, while Kawi specifies a '9' heat range for many KDXs, lots of riders (if not most) have switched to an '8' without detriment.

Kawasaki also specifies jetting that is way off, so its up to the rider to tune his bike for what works best for him. Plug heat range is just one variable.

Kawi sells these bikes worldwide, and fuel varies significantly, which might partly explain their jetting and choice of plug.

In a trail bike that is frequently operated at low rpm, it is my experience a hotter plug is less likely to foul on the trail, with the jetting being equal.
 

Matt90GT

Member
May 3, 2002
1,517
1
I dont keep up on the 200/220 specs but if it is like the kx65s, there have a LOT of different carb changes from year to year. Slides, needles, even carb sizes and brands at times with some models of bikes. thus could be another reason for the change in plug heat range.
 

whenfoxforks-ruled

Old MX Racer
~SPONSOR~
Oct 19, 2006
8,129
2
Merrillville,Indiana
The 60 has issues somewhere? Or the rider is loading the engine up? You can look at your plugs and determine if the heat range is good. The information should be at NGK or Champion. Does the 60 plug get real dark caked carbon at the end of the threads, wet and stinks? A colder plug will make the fouling worse at any rate. Vintage Bob
 

reepicheep

Member
Apr 3, 2009
670
2
More data for this thread...

I put in the replacement used coil (ebay from a parted out 2000). This replaces the cheap emgo (buddy had it on the shelf) that I was using, which replaced the bad original coil that was in the bike.

The lesson was:

1) A bad coil will foul any plug, after which no coil will help you until you replace the plug.
2) A $15 Emgo coil with a new plug will get you through the weekend, but will loose a lot of power.
3) A correctly working stock coil will flip you onto your back the first time you whack the throttle after getting used to bad original coils and cheap replacement coils.

The 60 is running like a scalded cat now. Yikes.

So the lesson here is that if you are spending too much time futzing with spark plugs, get over it and move on. Your coil is probably bad. :)

I probably will run a hotter plug in this bike though... it gets ridden on trails and around the cul-de-sac, no racing. I'll keep a few cooler plugs around in case he ever does MX or an Enduro. Plus I then have the same plug in my KDX and his KX, so I can carry a couple spares in the fanny pack and cover either of us having a bad day.

Thanks for the help all, I learned a lot!
 

Matt90GT

Member
May 3, 2002
1,517
1
i believe the misconception is that a hotter plug is a better spark or has more energy. That is not the case. It is the amount of heat removed from teh cylinder which has to do with the insulators in the plug.

Glad you got it working. OEM stuff is usually the best bet for electrical.
 

reepicheep

Member
Apr 3, 2009
670
2
Like common misconceptions about torque versus horsepower, that would be an easy wrong conclusion to reach.

If a cooler plug is not getting up to a high enough temperature to self clean, and is therefore getting fouled, switching to a hotter plug could give you a better and more reliable spark... so they might be reaching the right conclusion... but for all the wrong reasons. I hate it when that happens! :coocoo:
 

mudpack

Member
Nov 13, 2008
637
0
Spark plugs do not remove heat from cylinders. Hotter plugs do not cause overheating. The heat range of a spark plug is set to keep the plug hot enough to clean itself without the electrodes getting so hot that they cause pre-ignition.
Standard plugs like the one in our KDX200's have nickel-alloy electrodes. The expensive plugs like the ones in the KX-series bikes have precious metal electrodes which are much smaller diameter.
Spark plugs cannot add power, they can only cause misfiring which reduces power. A coil does not change power output; they either create a spark or they don't.
Lots of misconceptions floating around about those two components.
 

whenfoxforks-ruled

Old MX Racer
~SPONSOR~
Oct 19, 2006
8,129
2
Merrillville,Indiana
"If a plug is not getting up to a high enough temperature to self clean". This can happen for a few reasons, and has a few ways to work around it! BUT, fouling plugs for any reason is no fun in my book. That 60 is the quickest dirtbike there is, and about nothing for torque! Vintage Bob
 

whenfoxforks-ruled

Old MX Racer
~SPONSOR~
Oct 19, 2006
8,129
2
Merrillville,Indiana
If you detune the engine, there would be no issues with running the fat electrode/cheap plugs. As it sits, you can run a good chance of the ground strap falling off. The EG/EV series are good plugs, and not that expensive, they are just not 99 cents though? Going to buy the real expensive plug is not going to happen for me anymore either, the IEX? Well, until my grandson gets into racing, and he gets into the top 20 in the country! They are the best plug to resist fouling, run best on top, and the least chance of falling apart from sound and pressure waves inside the engine.
 

FruDaddy

Member
Aug 21, 2005
2,854
0
A broken electrode can give the entire combustion chamber a makeover (really sucks when it's a new piston). Mine was an EG I believe where the KTM wanted ECMVX$$$.

Usually, you can subtract 1 from the heat range if you do not operate the engine at high enough RPMs. I used to run a 7 plug in my KX250 because the 8 would foul within a week with me running a gear high almost all the time.
 

samiam

Member
Jan 3, 2000
46
0
I have found that the precious metal electrode plugs foul much easier than standard plugs. When I encounter and EG or EGV plug, (usually in one of my friends bikes that has fouled out and rolled to a stop in the middle of nowhere) I just replace it with an ES. The KTM "shorty" plugs are just plain stupid. They cost something like $24.00 and just give you a bit more room to work with.
To the OP - If I were you, I would just run B8ES plugs in both bikes. If you do not have that KX60 pinned for extremely long periods of time, you will be fine.
 

whenfoxforks-ruled

Old MX Racer
~SPONSOR~
Oct 19, 2006
8,129
2
Merrillville,Indiana
It truly is cheap insurance, believe it or not. You can "read" timing and heat range on the plug, maybe. Use the es plugs to jet with, or lower the compression/turn it into a kdx. OR, keep the top end fresh, and change the expensive plug every couple of races/ a reasonable facsimile. What does the book say for that bike, on hours for the top ends and plugs?
 

reepicheep

Member
Apr 3, 2009
670
2
"by the book" is pretty brutal... 10 hours of riding time until you replace the piston. I'm assuming that's "race use" for people that will be riding all out, and who want to bleed money.

I've been trying to turn it into a KDX...but it's a fussy little bike to keep running well. The Torque Spacer didn't help... but Eric Gorr's suggested porting (base of the cylinder) did. I think the way to turn it into a little KDX (which is what I want) would be to put a lower compression bigger bore kit on it. I wish somebody made a lower compression 100cc option... but that would probably have to be a stroked motor, which means a new crank, and probably just would not be practical.

I wish Kawasaki had made a more modern KDX-80 or KDX-100 type bike.
 

Dirtdame

Member
Apr 10, 2010
146
0
reepicheep said:
I wish Kawasaki had made a more modern KDX-80 or KDX-100 type bike.
Not likely for that to happen. All the kid sized trail bikes have to be of the "eco-friendly" four stroke variety these days.
 

FruDaddy

Member
Aug 21, 2005
2,854
0
The KX100 has been around forever, for the Supermini MX class. It is an 85 race bike with more motor. This will not likely help the OP is any way.
 

reepicheep

Member
Apr 3, 2009
670
2
Yup. This was my first (and probably last) high strung psycho supermodel primmadonna "race bike". Unfortunately there just aren't many other choices for a talented 10 year old that wants to do trails / enduro. He can handle an XR-80 just fine, but it's less power and a LOT more weight.

The KX-60 with a bigger gas tank, more CC's, and a less tuned motor would be a fantastic little bike. They *almost* had it.
 

glad2ride

Member
Jul 4, 2005
1,071
1
The stock plug for 1995+ KDX's is an NGK BR8ES, not a 9. B9ES is stock for '86 - '94 KDX200's.

If the KX60 is running properly, with a correct heat range plug and jetting, it should not be fouling plugs like crazy. Don't run a cheap plug to try to save money while taking a chance on the ground strap breaking off.
 

whenfoxforks-ruled

Old MX Racer
~SPONSOR~
Oct 19, 2006
8,129
2
Merrillville,Indiana
Every 60 I can think of is a rocket, isn't that kind of special? Lots of older 80/85 trail bikes around. As far as the 80's go, the XR is not that much heavier or slower.
 

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