help with plug fouling

millenko · Jan 13, 2002

hey guys,

I have 3 rides on my new KX250, to this point it's run great, but today I fouled 2 plugs in 2 hours.

I ran the kawasaki oil that the dealer gave me for the first tank. I ran out and had to buy some more, so I bought Motul (sp?). THe dealer said that it's the best. OK, fine, I'm looking to extend engine life so I'll pay a little more for it.
I filled up the tank with the last of my old premix, and ran it for an hour or two(with breaks) on the track. I pulled in for a break, then 15 minutes later fired it up. It started with no problems, one kick, and to that point hadn't had any problems with bogging or misfiring. It ran great!
I pulled out of the pits and hit the track, I gassed it and it bogged down terriblly, I pulled off the track and it died and wouldn't restart. I pushed it back to the truck, (I thought it had run out of gas). I filled it up with the new motul premix, but it wasn't out of gas. I kicked it and it still wouldn't start. I then changed the plug, and when I pulled it out, it was black and oil-covered. I put in the new plug and it fired immediately.

I thought everything was fine and ran it for another hour or so. I came back to the pits and filled it up, took a 15 minute break and went back on the track, it bogged and died again. I pulled the new plug and it was black and oil-covered also.

What am I doing wrong? I feel like I'm getting on it enough, there's very little spooge coming out of the tail pipe(very, very little). The bike runs great except for when the plug fouls. I run the premix at 32:1 like Kawasaki recommends.

What can I try to fix the problem? hotter plug? lean the mixture? play with carb settings? THe plug is an NGK BR8evx. going to a 7 makes it hotter right?

georgieboy · Jan 13, 2002

This is a familiar symptom. As long as you occasionally gas it WOT you won't notice the problem. The WOT cleans it just enough to clear the plug, but when you ride to the pit, walking pace it is not clearing for a few minutes it starts loading up. After eating lunch and filling her up, you notice the plug had been loading up.
The remedy could be you airscrew, turn her out, so leaning the mixture at 1/8 throttle. Or get yrself a leaner pilot.
Wait with the hotter plug (nr 7) till weather is frreezing cold.
I am using a 7 plug, but overhere it is 32F, and i am riding trail, so i need to keep it warm. good luck

whyz · Jan 13, 2002

I've had this same thing too.. Do you have good response from close throttle to wicking it quickly open?? if ya don't try turning in your airscrew all the way in snug not tight and then start turning it out starting at 1/2 turn and a 1/4 turn each time until you have a good response from close to open quickly.. turning it in will richen and out will lean.. if you have to turn it in more than 1/2 in you would need a bigger PJ, if more than 2 3/4 turns out you would need a leaner PJ. set it for response>> thanks Nic. But you probably know all this already too...
This was me.. Start up,let warm up,,take off,,FOUL.. Put new one in fine, for a while,until i take a break or something then it would do it again when i start it up.take off,,,FOUL! My turn for our moto, get there,turn bike off,wait 5 min. Our turn,start up,take off FOUL! Tried hotter plug,No change.
Got the bike Aug.30th new.. I have at least 30 or so plugs here since Sept.1st.(maybe more)and i was hurt from Oct thru 1/2 of Dec..so couldn't ride much.but rode anyway/Couldn't work either.Thought i could Fly but NOPE! I'm just obscessed My wife says..
Oh I even used the choke at the same time i had bogged it and it cleaned it up alot... we,ll since then I went 1 size bigger on the PJ.. No problems at all.
Then again our bikes are totally different.And so is the weather.
Good luck man,I feel for ya.
What gets me is if the PJ is lean,What cause's the foul?when you wick it open,say to a 3rd throttle opening?
There's alot more people with BIG TIME better answers than me who are the Guru's at this stuff and they can ride too.(I sure can't,I still think I can fly.)

James Dean · Jan 14, 2002

Jetting Problems and Solutions

-
The KX250 has a rich needle stock, NAFF. The clip position is probably what you need to change. Move the needle clip position 1 step leaner at a time until the plug fouling stops. There is a "TECH TIP" bulletin out from Kawasai that suggests you use needle N3WE (P/N 16009-1915). I have measured both and can tell you it is mostly just 2 clip positions leaner. (NAFF#1 is nearly N3WE#3)

James

(You will see this in the Excel jetting spreadsheet and guide, see: www.JDJetting.com , look at the examples for the types of graphs you can make to help with this on your own bikes.)

dix · Jan 14, 2002

You can only go one position leaner on the needle, and that's all you've got left. I went two sizes leaner on the main, 2 sizes leaner on the pilot and dropped the needle to it's lowest position, 2 turns out on the air screw, and it runs great. Also, don't be afraid to run a BR7ES. It's recommended in you owner's manual. My bike ran really rich with the stock jetting too, and I too fouled plugs like crazy at first. Only make your jetting adjustments one jet size at a time though, as all bikes are different, as so are there riders.

James Dean · Jan 15, 2002

And Another Thing!

dix is right, use the top clip if you want. It's close to what Kawasaki is selling you for the new and improved optional needle.

I spent $22 each for Kawasaki needles to measure and include in the jetting guide and spreadsheet, just to be complete and provide answers to questions like this. They are the most expensive of any brand. These stock and optional needles can be GRAPHED in the tuning guide to visually compare needle jetting effects-

NAFD,NAFE, NAFF, NAFG,
N3WD, N3WE, N3WF,N3WG

See your complete jetting with pilot, needle, clip pos., and main and compare it to a YZ or RM in the graphs. It may surprise you to see the difference. Even though the slide may be leaner, the pilot and needle are WAY richer.

www.JDJetting.com

yamadawg · Jan 15, 2002

move the clip to the top groove and run a br7e plug if you are just trail riding and pretty much keeping in the woods. If you are mxing then i would lean the pilot and main jets. Just dont make to many changes at once so it is easier to diffine what the problem was.

Kawaskis are naturally rich from the factory.

millenko · Jan 15, 2002

First of all, thanks for all the responses. I haven't responded to this point becasue I'm still trying to make sense of all the responses. I haven't had much experience (none) working with carbs, jetting etc... So I'm having to read R E A L S L O W!!!

You guys are making a lot of sense, but here's another question. I figured out today at work that I made a mistake and probably mixed the gas at 28:1...don't ask, it was early sunday morning and i was doing the math in the parking lot of the gas station.

would that 4 point increase in richness cause the fouling? I don't want to try and fix what isn't broken...

georgieboy · Jan 16, 2002

OK Millenko, let's assume that's the problem.
Allthough with the right plug, the plug wld be so warm it wld clean all deposits of any oil. And with the more oil you nade the fuel/air-mix leaner.
But just drain yr tank and put in a new batch fuel and go riding. That wld give you the asnwer.

help with plug fouling

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