KX125 97 fRIGGIN JUNK! ergg...need help

ellandoh

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looks like its time for :cool:

Spanky's jetting guide:

A correctly jetted carb makes a tremendous difference in the torque, midrange pull, top-end pull, and over-rev of your engine. If you have never jetted your bike correctly, you will almost certainly gain some performance at some point in the bike's powerband. A cleanly jetted pilot circuit can be the difference between having to clutch the bike out of a turn or not. The needle can make all the difference in the world for the power of the machine in most situations, as it controls the throttle range that most riders spend most of their time using. A correctly sized main jet could mean the difference between being able to rev out high enough to not have to shift one more time at the end of the straight, or the power falling flat on top and requiring you to make that extra shift.
Are you fouling plugs? Many people will tell you all sorts of band-aid fixes, from running less oil, to running a hotter plug. Both are incorrect fixes for plug fouling. It's all in the jetting.
The only way to know what jetting changes you will need is by trial-and-error. No one can give you jetting specs, because every bike is different, every rider has a different style, and jetting is totally weather dependent. Unless the person telling you what jets to use is riding an identical bike, on the exact same track, at the same time, his recommendations are meaningless.
Jetting is fairly simple, and is a useful skill to learn if you ride a two-stroke and want it to perform at it's best.
It's very important that you start with the pilot circuit. The reason is simple. The pilot circuit affects the entire throttle range. When you are at full throttle, the main jet is the primary fuel metering device, but the pilot is still delivering fuel as well, adding to the total amount of fuel that your engine is receiving.
Before you start to rejet your bike, you need a clean air filter, a fresh plug (actually you need several plugs to do plug-chop tests for the main jet), and fresh fuel. One important detail: Make sure the engine is in good mechanical condition. If your engine has a worn top-end, fix it first. Trying to jet a worn out engine is a waste of time. The same goes for reeds that don't seal properly, and a silencer that needs re-packing. Worn reeds will mimic rich jetting, and worn rings will mimic lean jetting.
Before you start the jet testing, install a fresh plug. Set the float level to the proper specs, an incorrect float height will affect your jetting all across the throttle range.
Warm the bike completely, and shut it off.
As already stated, start with the pilot circuit. Turn the airscrew all the way in, then turn it out 1.5 turns to start. Start the engine, and turn the idle screw in until you get a slightly fast idle, or hold the throttle just barely cracked, to keep the engine idleing. Turn the airscrew slowly in, and then out, until you find the point where the idle is fastest. Stop there. Do not open the screw any farther, or your throttle response will be flat and mushy, and the bike may even bog. This is only the starting point, we will still have to tune the airscrew for the best response.
Now is the time to determine if you have the correct pilot installed in your carb. The airscrew position determines this for you, making it very simple. If your airscrew is less than 1 turn from closed, you need a larger pilot jet. If it is more than 2.5 turns from closed, you need a smaller pilot jet.
Once you have determined (and installed it if it's necessary to change it) the correct pilot jet size, and tuned the airscrew for the fastest idle, it's time to tune the airscrew for the best throttle response. Again, make sure the bike is at full operating temperature. Set the idle back down (the bike should still idle, despite what you read in the Moto Tabloids), and ride the bike, using closed-to-1/4 throttle transitions. Turn the airscrew slightly in either direction until you find the point that gives you the best response when cracking the throttle open. Most bikes are sensitive to changes as small as 1/8 of a turn.
The airscrew is not a set-it-and-leave-it adjustment. You have to constantly re-adjust the airscrew to compensate for changing outdoor temps and humidity. An airscrew setting that is perfect in the cool morning air will likely be too rich in the heat of the mid-day.
Now, it's time to work on the needle. Mark the throttle grip at 1/4 and 3/4 openings. Ride the bike between these two marks. If the bike bogs for a second before responding to throttle, lower the clip (raising the needle) a notch at a time until the engine picks up smoothly. If the bike sputters or sounds rough when giving it throttle, raise the clip (lowering the needle) until it runs cleanly. There isn't really any way to test the needle other than by feel, but it's usually quite obvious when it's right or wrong.
Last is the main jet. The main jet affects from 1/2 to full throttle. The easiest way to test it is to do a throttle-chop test. With the bike fully warmed up, find a long straight, and install a fresh plug. Start the engine, and do a full-throttle run down the straight, through all gears. As soon as the bike tops out, pull the clutch in, and kill the engine, coasting to a stop. Remove the plug, and look deep down inside the threads, at the base of the insulator. If it is white or gray, the main is too lean. If it is dark brown or black, the main is too rich. The correct color is a medium-dark mocha brown or tan.
Once you have a little bit of experience with jetting changes, and you start to learn the difference in feel between "rich" and "lean", you'll begin to learn, just from the sound of the exhaust and the feel of the power, not only if the bike is running rich or lean, but even which one of the carb circuits is the culprit.
The slide is also a tuning variable for jetting, but slides are very expensive, and few bikes need different slides, so we won't go into that here.
Keep in mind, even though this article is intended primarily for two-strokes, four-strokes also need proper jetting to perform right, although they are not quite as fussy as their oil-burning cousins. The only real difference in the two is with the pilot circuit. Two-strokes have an air screw that you screw in to make the jetting richer, and screw out to make the jetting leaner. Four-strokes, on the other hand, have a fuel adjustment screw that you screw in to make the jetting leaner, and out to make it richer.
 

cnl83

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Nov 16, 2005
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well I took it off and it was kinda bent, but was droped all the way, so I bent it up and made it level. How do I get the gas out of the crankcase.
 

Colorado

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Apr 2, 2005
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cnl83 said:
well I took it off and it was kinda bent, but was droped all the way, so I bent it up and made it level. How do I get the gas out of the crankcase.

Getting gas out of the crankcase is done by laying it over and pouring it out or kicking like crazy 'til you clean it out.

Your float has a correct setting though. Both floats should be level, not leaking so they take on fuel, and set to a particular measurement from the carb body. I use a carpenter's tri-square for my Yamaha's (though there's some fancier thing shops use), but I believe my KDX manual says that I'm supposed to screw a special measuring tool to the bottom of the bowl and measure like a water level would.

According to Spanky's jetting above, you need to work on the float before playing with the jets. On some of my carbs the float tang is almost flat with the hinge metal whatever you call it, but on others it is bent way down. You really need to measure it and get it where the manufacturer says it belongs.
 

ellandoh

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cnl83 said:
well I took it off and it was kinda bent, but was droped all the way, so I bent it up and made it level. How do I get the gas out of the crankcase.

pull the plug and pretend to pushstart it, the bottom end will dry out
 

cnl83

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Nov 16, 2005
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Now, I got it to run, by kicking it a hell of a lot. Lotta smoke..and when I would let it die, try to kick it, and still wet. Should that have dried the bottom end?

I will try turning it or running it without the plug though.
 

ellandoh

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in my experience, starting and idling problems seem to come from worn(curled) , cracked or chipped reeds, and pilot jets

i would start by going through your carb put it back to stock and checking for good spark , put in a new plug , take the air filter off , looking for obvious problems, check the timing etc.
 

cnl83

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Nov 16, 2005
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Well it has a good spark, the carb is back stock (super clean). Will put a new plug, will get the gas out of the bottom end. I dont know how to check the timing, but will look into it.

Reeds...I got graphite reeds and one corner is a lil nibbled. Like barely de-laminating. Local mechanic said it shouldnt be that big of a deal.

I was messing with choke, and air screw (pilot) which could have loaded it up for me. I will post the results, and hopefully some poor soul will benefit from this in the future.
 

ellandoh

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sounds like its probably handled :cool: once you get it started next time , keep it running til its hot and wring it out a few times the smoking should quit then , then use spankys jetting guide to tweak iti a little
 

cnl83

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Nov 16, 2005
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No, I didnt try changing pilot jet at all. I figured that I would start from stock to get it right. Its just that I have a DG pipe, FMF silencer, but do not have the stock pipe.
 

ellandoh

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nickyd said:
go to FMF's website - they should have jetting RECOMENDATIONS in the technical section for your bike

fmf is waaaaayyy off for my bike, they copied mxa rec's but left out the part for the larger cutaway :bang:
 

cnl83

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Nov 16, 2005
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Dog on it!

:bang: :Man, I went out there tonight, and I took the plug out, and cranked on it to get the gas out, nothing came out, so I pulled it behind my blazer slowly and nothing came out. I turned it upside down, and nothing came out!

So I cleaned the carb, and it would not start, changed the plug, made sure it had fire. I took the carb off and shot carb cleaner lightly, kicked it and it started right up, and of course just died. So I know the engine is good, and its a fuel issue. I took the carb down, put new jets, cleaned it thorougly. Three of us cleaned it! We all took turns! Stared at the pieces for about 20 minutes to make sure we were not missing anything. Put it back together, and it would not start! I shot carb cleaner in the breather, cranked up, and of course same problem, wont idle, and runs like poop!

Tommorow im going to try and get new fresh gas 30:1. Im 40:1 right now. :bang:
 

ellandoh

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that change of ratio will do nothing unless lightning strikes in the snowstorm or your gas is very old, try taking the drain plug out of the carb and gas should pour out causing your float to open and continue to pour . to be sure you are getting gas. check that none of the carb vent lines are clogged.
take your pipe off and fill it with water and make sure no mice got it as a home.
that all i can think of for now besides checking timing??
 

cnl83

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Nov 16, 2005
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Crying...

I took my engine down, I need new piston / Rings / cylinder / and rod! ERGGG

lotta money...anyone know where I can get my cylinder re-nickeled for a good price?
 

usgpru27

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Jan 15, 2005
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I had the same problem with my CR125 this spring after getting it last winter. I recommend that you richen up every circuit. Go up on the main, raise the needle, larger pilot and close the air screw to 1 turn out. Then start to lean it out starting with the main. I was just like you and really pissed. I roadrace a 125 2 stroke 125 and was trying to tune it like that. They run as close to meltdown as you can make it. These dirtbikes like to be a little on the rich side.

Just ride with a few new cheap plugs as they will likely foul really rich. Not sure where you are in the country but if you are in the cold weather you are also just chasing the weather. As it is getting colder you need to get richer.
 
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