kx 250 plug killer

[greendragon70]

Hi folks,i really need some help with my '87 kx 250,the bike is eating spark plugs,they last no longer than half an hour!the bike runs fine then it seems like the plug fouls, it wont go again unless i fit a new plug,it makes no difference cleaning the plug and if you put an electrical tester on it shows the plug has broken down!it's starting to get expensive and very inconvenient!I'm running a 40:1 mix with castrol tt and i'm not plodding around its getting plenty of revs most of the time,as i sais before when it's running it has loads of power up an down the rev range,i'm at my wits end thanks in advance!

 

[pimprn]

Hi i read in other posts, something similar to this i think it has to do with your jetting, or change ur spark plug to a 9, or your fuel mixture. im not sure which one but its one of thsoe :D

 

[John Cena]

Id say your jettings off somewhere. Does the bike smoke alot when warm? When was the last time the air filter was cleaned? How do the plugs look after riding all black and oily? What heat range plug you running?

If your running a br9es plug your might want to try a hotter plug like br8es.

 

[BSWIFT]

Read the thread at the top of this forum and follow AND read the links in the thread. Jetting is not hard, its tedious, slow and boring. The best part is that you can do it and you will know your bike even better. When you get it right, you will feel the difference. The price for jets is cheap, a few more brand new plugs, BR8ES and follow the proceedure until its right. One of the best learning experinces you will have with your bike.

 

[greendragon70]

still killing plugs

Thanks for the replys,could someone explain to me the meaning of plug fouling ,is it when the plug gets dirty and won't spark or like with me the plug is broken ?it won't spark after cleaning ,if i put a tester on center electrode and plug thread there is a short circuit!The bike behaves well with a new plug and it has been jetted correctly im beginning to think it has something to do with the ignition,thanks again in advance!

 

[BSWIFT]

Plug Reading - What does a good plug look like? First you need to know where to look and what to look for. I’ve seen a lot of plug reading instruction that suggest you to look at the general appearance of the plug. That doesn’t work. The easily visible portion of the plug, the upper part of the porcelain and the electrodes, won’t give you an accurate reading. This area is mostly affected by additives in the gasoline and the oil you’re running. To get an accurate indication you want to look down inside the plug where the porcelain insulator emerges from the steal body of the spark plug. Ideally you should see a ring of light brown/tan at the lower 1/4 of the porcelain. White is lean and you’ll need to install the next richer main jet( larger number ) and do another plug reading. A dark brown to black ring is too rich and you’ll need to install the next leaner main jet ( smaller number ). A small flashlight and magnifying glass make this much easier to see and it’ll give your friends something to poke fun at. If you ride in a diverse area with fluctuations in temperature greater than 15 degrees F, and altitude changes dropping more that 3000 feet over the course of the day or you ride in high load conditions ( loose sand, mud, long steep hills ) adjust the size of your main jet until you reach the ideal condition then install the next richer main jet which should result in a dark brown plug reading. You'll be loosing a small amount of top end power in trade for the added confidence that you can ride aggressively over the course of the day without fear of running lean at WOT.

 

[newfie125]

plug fouling

hey i had the same problem with my 2005 cr125R and i called the dealer where i bought the bike and they said let the bike warm up for about 10mins or turn the gas off until the bike starts to cut out and that should work. i tried it and my problems were solved, i use to go threw about 10 or 12 plugs a week, try that to see if that will work

 

[Britt Boyette]

Jetting is something we all must deal with. It won't mean much if all else is not well. Check for a clean airfilter, be sure your float level is correct and that your float valve is fuctioning correctly, and that your carb is clean. Also, check that you don't have a worn out reed valve and that your compression is within spec using a leak down tester. You could also try a hotter plug such as the BR7ES to see if it makes any difference. Sometimes it does.

 

[Kevin003]

Id almost just drop the main jet a size or two and see what that does for you. If you do this make sure you check your plug to make sure your not lean.

 

[greendragon70]

Kx compression and plug type?

Thanks for the help everyone,i checked float level,valve ,reeds,cleaned carb,i did a compression test with throttle open which was 203psi? i don't know if thats what it should be! also would using a non resistor plug make any difference?Thanks in advance!

 

[nikskx]

Hey I am also going through the same problem, I was just blaming it on the change in temperature. But i may end up buying some 8es plugs this sunday. Does a clean filter really make that big of a difference??

 

[Britt Boyette]

Umm, yes.

 

[mtk]

So does air temperature changes, and barometric pressure changes, and relative humidity changes for that matter.

Jetting isn't a "set it and forget it" item.

 

[greendragon70]

203 psi compression is enough?

 

[just_a_rider]

Clean unrestricted air in and unrestricted exaust out. 87 model could have a nearly stopped up silencer<----this can also foul plugs. I found this out when my boy held his hand over the exaust while my kx250 was at an idle. the bike cut off and when I went to crank it no luck, had to grab my spare and put it in and it fired right up.

 

[griffbones]

If this bike had been running good with the current jetting and just all at once started eating plugs, I think I may know what is causing this!

Let me guess, with a new plug it runs really good with no misses or ills at all, then all at once it just dies. You pull out the plug and the thing is just completely black and wet!

On our old CR60 we had a pulse coil in the stator assembly go bad and it caused these very symptoms. Up until that time the plug ran a nice tan color and we never fouled a plug ever! Then one day it started eating plugs like every thirty minutes, then after about five plugs it would no longer fire at all. An ohm meter test showed an open pulser coil in the stator. I replaced the coil and the bike was back to normal and has never fouled a plug again (in two years)! Jetting would have to be way off to eat a plug in thirty minutes, that is why I think you may have the same problem that I had with our old CR60.

I also have a friend with an old Yamaha TT500(4 stroke), he would ride about 100 yards and the bike would just die. Pull the plug (black and wet), install new plug, fired up on first kick, ride 100 yards same thing! It turns out he also had a pulser coil going bad. He swapped out the stator assembly for one out of another old TT500 and he was back in business!

Also, you state that you are using a non-resistor type plug, this can sometimes play havoc with the CDI, so put a resistor plug back in the bike and try that first.
I Hope some of this is a help to you.

 

[husabutt]

Carburetor needles are wear items. As they wear the jetting becomes richer. Based on the age of your bike there is a good chance this has occurred. Replace the needle jet and the jet needle as a set. Kawasaki lists 4 optional jet needles for your bike. The jet needle is the part the needle jet goes into. I would be inclined to possible go one size leaner. Also your stock main jet is a 350. Try a 340.

Your oil/gas mix ratio will have very little effect on plug fouling.

Going to a hotter spark plug will only mask the problem for a little while.

Proper carburation and jetting will give you better performance and stop premature spark plug fouling.

 

[greendragon70]

Thanks griffbones! and everyone else you have been very helpful, it was the stator coil ! i replaced it and no probs since ,loads more power bike now wheelies in 3rd gear downhill!

 

[griffbones]

Glad to hear you got this sorted out! :cool: