KX Riders
Maintenance & Technical => KX250 / KX125 => Topic started by: mxrider503 on May 01, 2005, 09:48:13 AM
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:evil: My bike eats spark plugs like they are some kind of dirtbike candy. I have to keep a few with me just for a couple hours :( Per my other forum post labeled "My KX250" I thought I had the kinks worked out. I pulled the first plug after an hour maybe two on friday night and it was fouled like a mofo. I turned the airscrew all the way in and brought it out 2 and a half turns plus another 1/8th of a turn because of how fouled the plug was and to my dismay this pig still ate it after about an hour of riding on a fairly rainy next day. The guy who owned the bike before me said he ran race gas because he upped the compression and he ran br9es ngk plug. However he has yet to supply any specs on compression ratio and other important details (i don't think he knows enough to have done this work) so I ask you dirtbike fanatics to help me in solving this annoying problem. Also the second plug i pulled out looked perfect aside from some excess black all around (spot of tan in the middle). Is this a good plug to run? Will changing the jets in my carb adverslely affect my bike if the compression is infact upped and if so what jets would you suggest and where can I get them quickly? If the bike compression is higher, would running race gas solve this fouling issue? Thanks in advance for your replies.
-brian
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Have you seen these informative pictures; http://www.ingfatrygg.se/Spark_plug_diagnostics.html ?
//John
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I would also run a compression check. When my 2-strokes start eating plugs, I usually am due f or a fresh piston.
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good advice john but doesn't really help me other then i can tell you guys that it is a dry carbon buildup possibly from a cold running plug. Any suggestions for a more appropriate plug?
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Since its eating gas and plugs Itd be safe to say its jetted to rich,try one change at a time and take notes on what effect they have.If the compression is to high for the fuel your running itll "ping",and itll ping if your jettings lean,but then you wouldnt be eating gas and fouling plugs,so if its pining try 1/2 race gas and pump gas.Now normally you go by "low range","mid range"and "top end" when it comes to basic jetting,then you can fine tune later.Start with low,does it start ok and run strong up to 1/8 throttle?Being that your out 2 1/2 turns on the air screw you may want to pull the carb and the pilot jet has a # stamped on it,go down one # size try 1 1/2 turns on the air screw and see how it runs.Check the float level,this can really affect mileage (fuel running out the overflow lines) and how the bike runs (especially in the rough).Then for 1/4-3/4 throttle check the clip on the needle,being you seem to be rich try raising the clip a notch.For 1/2 to wide open try a leaner main jet,check the # stamped on the one in the carb and try one # smaller,be carefull testing with a leaner jet (especially the main),dont want pinging/rattlig sound or to seize the bike,itll run hot and can feel like its running out of fuel if to lean (better a little to rich).I normally mail order my parts,but your local dealer will be faster if there in stock,as far as the plug ask for what the bike runs stock and go from there.Remember one change at a time (as time consuming as it may be),take notes for referance,ask here for help,and humidity,altitude,and temperature all effect jetting!A manual is worth the money or even the owners book can help,but dont be scared to ask someone here for help.
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good advice john but doesn't really help me other then i can tell you guys that it is a dry carbon buildup possibly from a cold running plug. Any suggestions for a more appropriate plug?
Sorry I just noticed that its a "dry carbon build up",but I would still try my above post being its eating gas and Id need to see the plug as far as the fouling.Hope I was some help.
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whew! lotta stuff to consider. Just to be sure as somebody said differently my air screw is the brass one next to the intake and the idle is the black plastic one kind of positioned at the bottom of the slide. Also just to let you know i had a problem with the float before and i took it apart and and adusted the "tang" I believe its called. It stopped leaking gas through the over flows when it was off and or idling. However would adjusting it too far also cause it to leak gas? or perhaps could that be the issue with the plug. Because I've noticed with that adjustment to the airscrew I said before, has definitley helped my bike performance. Also just to let you know what happened on saturday when I was riding. I hit the gas hard as I let the clutch out hoping to rooster tail the hell out of my buddy and his Xpar 200 but to my dismay the bike just died. Then the second plug was replaced when I was just sitting waiting for my buddy to catch up with the clutch pulled in and I was in first gear and it just died. Sure enough a new plug solved the problem and I started my bike up yesterday and it ran better then it did on saturday. Insanley touchy and I couldn't keep my front wheel down! Ill try another tinker session later this week. As far as the plug goes I'll see if I can get some pics up here as I have never posted pics in a forum. I am definitley curious about that float so please get back to me :)
Thanks,
-brian
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also what is the typical gas mileage of a kx250? i have one of those larger img gas tanks and it goes through half a tank about 1.5 gallons in about an hour of not even consistent riding.
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also is the float supposed to allow dripping while the bike is running?
-brian
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You may be finding your problem. Their should be no fuel dripping from the vent lines with or without the engine running. You could have a worn needle or seat or just incorrect float level.
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also what is the typical gas mileage of a kx250? i have one of those larger img gas tanks and it goes through half a tank about 1.5 gallons in about an hour of not even consistent riding.
Your right,your bike sucks gas!Now depends on riding style and terrain (like snow,deep sand,deep mud) but if your leaking fuel out the overflow as Hughes said you should get a needle and seat, check that the floats do float and are not sinking from a leak in them,adjust your float parallel to the carb body as you hold it upside down with the float causing the needle to just touch the seat (not sure for a 250,but try 17-19mm) If you adjust it to little you will have fuel leakig out the overflow and bike loading up,to much will starve the bike for fuel.You still may have jetting issues but one thing at a time,sometimes you bang your head against the wall over a simple little problem.
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yeah if the bike is running its either on or off in my opinion so that could be the issue but it does still drip gas. I did adjust the tang before but the needle that gets pushed by the float did look just a little worn. It is very frustrating to always be tweaking. Could this float problem contribute to the spark plug fouling? Also I have a mud fetish so u'll usually find me in the mud pits at the trails. I would expect more gas to burn under these conditions but a tank should last at least 2 days of riding or close right? Ill take the carb apart and see what I can fiddle with :) thanks and anymore advice is appreciated. By the way im looking to get a few other kawi guys out here riding with my buds and I. So if your somewhere close to CT and you want some problem free riding I'd luv to stick it to a few cr punks out here. :evil: :blowup: :blowup: :blowup: :blowup: :blowup: :blowup: :blowup: :blowup:
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Brian,
You can use the air screw (the brass one at the bottom of the air intake) to tell if you pilot is off. Start with it one to 1.5 turns out. If throttle response is better when you turn it in, you need to a bigger pilot. If it runs better as you turn it out, you need a smaller pilot. If you're within the range of 1 to 2 turns out, and achieve the best throttle response, your pilot is spot on. Pilot jetting is most often the cause of fouled plugs, if the top end is good. Worn top ends can cause fouled plugs as well. As stated before, the clip position affects around 1/8 to 1/2 throttle, and the main jet affects 1/2 to wfo. If the bike isn't gurgling or bogging up top, then the main is probably okay. throttle chop testing is a way to verify main jets, but I've never done it myself. If you have fuel running from your overflows, you either have a piece of dirt in one of the orfices, or the float height is set too high. try using comp[ressed air or running a small piece of solder up through the orfices. As mentioned before as well, if the needle and seat are worn, you could get excess gas in the bowl as well, and would create a rich, plugfouling, overflow dripping situation. Hope this helps.
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yeah if the bike is running its either on or off in my opinion so that could be the issue but it does still drip gas. I did adjust the tang before but the needle that gets pushed by the float did look just a little worn.
If the bike is leaking gas and the float needle looked a little worn.....your problem is staring you in the face. Change the float needle, and reset the float level. This problem alone can be the root cause of all your woes.....do not look to jetting until the float is set properly.
It is very frustrating to always be tweaking. Could this float problem contribute to the spark plug fouling? Also I have a mud fetish so u'll usually find me in the mud pits at the trails. I would expect more gas to burn under these conditions but a tank should last at least 2 days of riding or close right? Ill take the carb apart and see what I can fiddle with :) thanks and anymore advice is appreciated. By the way im looking to get a few other kawi guys out here riding with my buds and I. So if your somewhere close to CT and you want some problem free riding I'd luv to stick it to a few cr punks out here. :evil: :blowup: :blowup: :blowup: :blowup: :blowup: :blowup: :blowup: :blowup:
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Just a thought... I have a 99 KX250, the specs call for a BR8ES plug, you are running a 9. The plug may not be hot enough. Depending on the riding I'm planning, I will run either an eight or a seven. If I'm heading to the track, I run an eight. If I'm out with a bunch of guys on their 4 wheelers, and will be slow wood/trails, I'll run a seven. I've had the bike to almost 2 years now, and only fouled 2 plugs. (both times I forgot to switch to a seven before hitting the trails.)
My bike is still running a little rich, I need to drop one notch on the clip, but I've been lazy and haven't gotten to it yet. After I change the jetting, I'll probably stay with the BR8ES plug.
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ust a thought... I have a 99 KX250, the specs call for a BR8ES plug, you are running a 9. The plug may not be hot enough. Depending on the riding I'm planning, I will run either an eight or a seven. If I'm heading to the track, I run an eight. If I'm out with a bunch of guys on their 4 wheelers, and will be slow wood/trails, I'll run a seven. I've had the bike to almost 2 years now, and only fouled 2 plugs. (both times I forgot to switch to a seven before hitting the trails.)
My bike is still running a little rich, I need to drop one notch on the clip, but I've been lazy and haven't gotten to it yet. After I change the jetting, I'll probably stay with the BR8ES plug.
Good point on the plug....I use a BR7ES since my riding is typically slow on the trails....my bike runs perfect and I do not foul plugs.
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Use the EIX plugs. Even with a bike horribly jetted it usally lasts a season.
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ust a thought... I have a 99 KX250, the specs call for a BR8ES plug, you are running a 9. The plug may not be hot enough. Depending on the riding I'm planning, I will run either an eight or a seven. If I'm heading to the track, I run an eight. If I'm out with a bunch of guys on their 4 wheelers, and will be slow wood/trails, I'll run a seven. I've had the bike to almost 2 years now, and only fouled 2 plugs. (both times I forgot to switch to a seven before hitting the trails.)
My bike is still running a little rich, I need to drop one notch on the clip, but I've been lazy and haven't gotten to it yet. After I change the jetting, I'll probably stay with the BR8ES plug.
Just a quick qustion....Are you saying that the BR7ES is hotter than the BR8ES?
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Yes the BR7ES is hotter then a BR8ES. The lower the number, the hotter the plug.
The bike was designed to run on the 8, but depending on riding type, I'll switch between an BR7ES and an BR8ES, but usually run a BR7ES.
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Since I run mine is sand, I'm running a B9. Non-resistor, If you have a pace-maker, stand back!
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Posted on: August 21, 2006, 12:39:11 PMPosted by: Arigato
Insert Quote Since I run mine is sand, I'm running a B9. Non-resistor, If you have a pace-maker, stand back!
As Arigato pointed out, depending on riding style you may need to adjust how hot of a plug you run. He's in the dessert WFO running a 9. If I'm running a track I run an 8 (because I'm too old and slow to keep the throttle pinned), but if I'm in the woods busting trails, I'll drop to a 7. My jetting is a little rich, (because that's how I like it) but I've only fouled 1 plug in 2 years. Another problem can be your pre-mix. Find a pre-mix brand you like, and stick with it. Switching brands can wreck havoc on jetting. Jet properly, and have fun.
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Get the float set first. A little fuel spilling out when leaning the bike over a bit is OK. Most racers have the float set to give a little more fuel in the bowl than stock, more supply for wide open throttle (WOT) and when laying the bike over heavy in turns. Some even purchase a bigger aftermarket bowl or mod the stock one for modified motors using lots of fuel.
Put in a BR8E(G)(medium duty-fine wire nickle) or BR8E(V)(race duty-fine wire gold platinum), instead of an BR9E(S)(standard duty-copper core). This will give you a better quality plug to work with and less fowling with longer duty life. The lower number is hotter and larger number is cooler. Dunes 9, track 8, woods 7, so to speak.
Then start working on the jetting. The airscrew really only helps the pilot system (idle to 1/8 throttle) and up to 1/4 throttle where you are just getting on the needle. So see where your main jet is at first (WOT running good with throttle chop and a plug check) and work back the two steps (needle clip and pilot jet-air screw). Of course this is a quick overview of the steps. Start at the top.
Sly