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Discussion Starter · #1 ·
My question is kind of general. It is a 2003 KX125 that I got a few months ago.
When accelerating in 1st and 2 gears it seems to get very loud but not much response to back wheel. It isn't a very fluid type of loud like you would expect, more like it is choking, then it seems to grab and go as you would expect. As you get in to the end of 1st or the end of 2nd it gets normal and 3rd on is OK. But 1st and 2nd gears seem to be choking out, loading up, not quite sure how to put it in terms. Can anyone tell me if this is a clutch issue, jetting issue? To be honest I can not tell by the engine sound. I was told by the guy I bought it form that it was jetted for racing and I need to get on it hard in the low gears or it will "load up" as he referred to it. Is this normal? Can anyone diagnose or explain? The bike starts first kick and seems to have very good compression and no other issues I know of.
 

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i have the same year model bike and mine did the same thing it seems as though you have the choke on right ...... then once you run it hard about 1/2 -3/4 throttle it starts to clear up then it takes off right...... welll i turned my air mixture screw in about 1/2 a turn and mine cleared right up mine was also a little rich on the top side ( it was spittin ALOT of oil out the exhaust) so i also raised my clip on the needle one position and mine runs like a raped ape now ......... also it proabbly wouldnt hurt to repack the muffle its pretty cheap to do and it is really easy to do just a little messy is all i picked up so MSR packing at my local shop for like 6 bucks i think and believ it or not but just repacking the silencer helps out a ton
 

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Discussion Starter · #5 ·
money. I will try those in order, you decribed it better than me but that is exaclty what mine does. I know the silencer need repacked, but it is riverted so i didnt want to get into it. It does do a little spitting too.
Thanks alot.
 

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well when you do them start with the air screw first and only turn it about 1/8 to 1/4 turn at a time and make sure it is warmed up to operating temp first then after you adjust it once then ride it for 10-15 min then you should see some sorta change it maybe real small but you should see something and keep making small changes until it runs the best but DO NOT go to the clip until the air screw is set right ..... the air screw will clear ALOT of your symptoms up but always make one adjustment then ride make another adjustment ride and so on and so on ........ and if it gets worse after a adjust ment just undo your last one you made and your back to a clean runnin bike

also the air screw if i rember right only helps idel to 1/3 throttle it maybe half .... but either way it helps at the lower rpms
 

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Discussion Starter · #7 ·
Sorry,
I didnt realize that two different peope responded. I am open to any advise or hints. I love to ride them but know absolutley nothing about working on them.
 

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Yes, always adjust it while the bike is running. How much experience do you have on MX bikes? Are you keeping it on the pipe constantly, or are you doing a lot of low RPM riding?
 

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Discussion Starter · #10 ·
I am 38 and havent ridden a 2 stroke in 20 years. This is actually my first dirt bike in 20 years. My kids have 4 strokes so I sold my road king and bought this to ride with them. I should have got a 4 stroke.
Not sure what "keeping it on the pipe" means, but yes, I putz around at low RPMs some times.
 

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"Keeping it on the pipe," refers to keeping the engine in the RPM range that the engine creates the most power. When you roll on the throttle, you will feel a point where the engine starts to "sing" and it starts pulling real hard. That is when you are on the pipe. Many times, these two strokes will load up(The engine cant burn all the fuel it is getting) at low RPM because of their tuning.

When you are adjusting your air screw:
-Start at 1.5 turns out.
-Turning the screw out makes leans the mixture out between idle-1/4 throttle.
-If you have to go farther than 2.5 turns out to make the bike run properly, the pilot jet needs to be replaced with a smaller jet.
 

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Discussion Starter · #13 ·
So let me get this straight. Regardless of where the airscrew is now. reset it to 1.5 turns out? Or go from where it is now? If so, in or out?
 

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You can just go from where it is at. 1.5 turns out is just a good starting point.
Just adjust it at 1/8 turn increments from where it is.
 

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Discussion Starter · #15 ·
Ok. Tried to adjust. Seemed to be best where it was. Funny thing. It
seems like now every time I try to get on it it stalls out. It started
before I even tried to adjust it. When I was getting it warmed up to
adjust it, I could idle it all day and even rev it up. The minute I tried
to get on it it would stall instantly and would not start without
cleaning the plug. Did that many times. The plug was new, the air filter is
clean. Could it be the fuel? Although I did ride with that fuel for
a couple of hours. The plug seemed to be oily and had to be dried. Any ideas. Could it be compression. How could tell if it is compression?
 

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Drain the carb and tank, then mix up some fresh fuel. If you dont have a huge jug of Silkoline to get rid of, buy some AMSOIL Interceptor or Dominator and mix it at 42:1.

-My bike gets cranky and doesn't like gas that is much more than 2 weeks old.
 

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i have the same year model bike and mine did the same thing it seems as though you have the choke on right ...... then once you run it hard about 1/2 -3/4 throttle it starts to clear up then it takes off right...... welll i turned my air mixture screw in about 1/2 a turn and mine cleared right up mine was also a little rich on the top side ( it was spittin ALOT of oil out the exhaust) so i also raised my clip on the needle one position and mine runs like a raped ape now ......... also it proabbly wouldnt hurt to repack the muffle its pretty cheap to do and it is really easy to do just a little messy is all i picked up so MSR packing at my local shop for like 6 bucks i think and believ it or not but just repacking the silencer helps out a ton
i dont want to steal bodes thread but this is exactly how my 03 kx 125 is.....it even spits out the oil everywhere.....im waiting on getting muffler packing but my local shop was out.....once i get it im gonna throw it in...put in a new spark plug clean the carb and try what you did to yours....im starting to get an idea of how this jetting works after reading the manual and reading a guide online....my bike at idle even sounds deep and raspy...so im gonna try this and see what happens...hopefully i can get this done on wednesday cause friday night im going riding up in jersey with my buddies...they all ride quads....thanks
 
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