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Discussion Starter #1
Hey all so as you know i picked up my 03 125.....the bike bogs in first gear like if i am riding it slowly then just gas it...it doesnt just scream and jump right away.....also i can be speeding like crazy and the bike is running good throughout the gears then i slow down, putt around for a couple seconds then try to take off again and it sounds like a 2 stroke sounds when you first take off to go and warm them up......it hesitates for a little....i dont know if this is because of the cold weather we are having or if it needs to be jetted.....im sure it needs the jetting but if not can anybody tell me what it could be? and if its the jetting can you guys explain to me like what size jets i would need cause i have no idea about that...
 

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I assume its a stock bike. You should know what the bike is set up for before you start to play with the jetting. ie what pilot jet is in it and turns position, needle clip position and what main jet you have. Although a quick tinker with the pilot jet may get results (start at 1.5 turns out). Other posts here refer to "Spankies Jetting Guide" its a good read.
 

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Discussion Starter #5
I assume its a stock bike. You should know what the bike is set up for before you start to play with the jetting. ie what pilot jet is in it and turns position, needle clip position and what main jet you have. Although a quick tinker with the pilot jet may get results (start at 1.5 turns out). Other posts here refer to "Spankies Jetting Guide" its a good read.
1.5 turns out...?? i thought the pilot jet was inside the carb....im not good with jetting cause i never did it before....i do have an owners manual tho idk if that will help me....
 

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Yeh, you got me there, the pilot jet meters the fuel for the pilot circuit and is a fixed size and can be changed by replacing it with a different size, and the air screw adjusts the air mixture for the pilot jet and is usually 1.5 turns out for starters. The pilot jet is for the initial throttle opening and is what gives you a snappy response when tuned well. This needs to be adjusted (in richer, out leaner) whenever you have a big altitude change or temperature change. The owners manual gives you a good idea on jetting but "Spankys Guide" is good for the adjustments.
I had a similar problem like your bike when I had the needle clip too low and it ran rich. Symptoms were severe bogging at the bottom end but ran good well into the power band and it wasn't easy getting into the power band coming out of a corner. I just raised the needle clip by one notch (leaner)and the bike was transformed.
Only change one thing at a time and test the result. Be careful really lean running means a new motor rebuild.
 

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Discussion Starter #7
well i went to pep boys and bought some carb cleaner so tomorrow i will take it apart if i have time and clean it up and throw a new plug in it...i will see what happens...if not then i will put the air screw 1.5 times out and see what happens......if thats not it where can i order jets...i definately think the bike is rich because the oil dripping the silencer...it goes all the way down but i know alot of 2 strokes do this...the thing that is weird is that my bike manual says the bike is jetted for sea level and i am not that far above sea level...actually pretty close to it so i dont see why jetting changes would be needed....it seems pretty easy to find the jets but just knowing which jet to put in is the hard part...and is this spankys jetting guide online? thank you
 

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If the bike is spoogin out the exhaust then repack the silencer. It could also be a bad right side crank seal as it's sucking tranny fluid into the motor. If the jetting fixes the problem then your better off then a bad crank seal. If it's a crank seal then the motor has to be split to change it.
 

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whoa, your like a bull at a gate here! From what you said I read it that you can get in the power band once it gets out of its bog area and it pulls all the way to the top rev range ok, if so then the prob is low to mid. What I would try is set the pilot jet screw to a start point 1.5 turns out (or what the owner manuals says since its an '03, I have an '02 kx125) and also raise the clip position one notch. This will lean out the mid range. You should notice a drastic change. Before you do this repack the tail pipe and use a new plug
There are so many variants in jetting you need to read your manual first to get the idea of what is happening within the carby. It gives you a trouble shooting guide, failing that go to the bike shop and find that 2 stroke guru (now days he's the old guy shoved down the back drinken' beer hidden by the four strokes bikes)
 

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Discussion Starter #10
owners manual says 2.5 turns on the screw.....
 

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Sounds like a lean condition already on the bottom end, don't worry about the spooge until you get the jetting figured out. If the bike is sitting on the stand, and idling, if you quickly crack the throttle does it bog? If yes then you can turn IN the air screw that wil richen it up, if that helps then you'll need a richer pilot jet. As the temp outside cools down you'll need to richen the jetting, unless of course it was already to rich.

The other issue with a 125, you have to be in the right gear, if your in to high a gear and you wick the throttle, it'll bog.
 

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Sounds like a lean condition already on the bottom end, don't worry about the spooge until you get the jetting figured out. If the bike is sitting on the stand, and idling, if you quickly crack the throttle does it bog? If yes then you can turn IN the air screw that wil richen it up, if that helps then you'll need a richer pilot jet. As the temp outside cools down you'll need to richen the jetting, unless of course it was already to rich.

The other issue with a 125, you have to be in the right gear, if your in to high a gear and you wick the throttle, it'll bog.
+1:wink:
My son's KX100 had a 45 pilot jet and I had set the air screw to only one turn out once the temps had dropped down to about 50 degrees this fall, yesterday with 32 degrees temp it wouldn't idle or respond worth a crap off of idle unless the air screw was set to only about 1/2 turn out. Solution - I went to a 48 pilot jet and then opened the air screw back up to about 1 1/2 turns out, Results - perfect idle and great throttle response.
 

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I have a 2004 KX 125, I went from a 40 to a 37.5 on the pilot. This is what Team Green recommended. After that I went from a 32:1 to a 40:1 fuel mix .
Then I went to a NGK B8ES instead of a BR9EIX plug. My bike really screams for now. I still get a little spooge out the exhaust though.

Ron A.

 

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Here, I remembered Bill's Pipe's website had jetting info.

KAWASAKI KX 125 (2003) WE SUGGEST
MAIN 410
PILOT 37.5
NEEDLE STOCK
CLIP 2nd
AIR SCREW STOCK

I used Bill's recommended jetting on my bike, and it works pretty good.
 

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I would clean carb and go and do Spanky's guide to jetting it help me to get my bike to the best performance. Repack the muffler also and if the top end is worn out I would recommend doing a top end. A worn out top end will give you false readings.
 
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