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my 125 is having some problems!

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I just bought the bike probably a few months ago and its been gettting worse.   2002 KTM 125 SX

but here is what is happening:

bike starts and idles fine, ill let it warm up and start to ride if i give it just a little bit of gas im fine, but once i open it up about half way (still in first gear) it loses all the power kind of like its bogging,  but if i hold it wide open long enough it will eventually hit higher rpms into the powerband and run normally, and then the same thing happens when speeding up from corners, jumps, etc. it never dies or anything...

Im mixing my gas with 93 octane and 32:1 belray I have not done anything to bike, its all stock as far as I know

 

 

my next problem is in the forks, if i hit any jump i can feel the forks "pop" and lag a little bit mid air.

 

Im in the process of putting a fresh top end on it, I can see light thru the reed petals (i was told they need replacing because they need to be completely tight on the block not allowing light to pass...can someone confirm that)

Also, the power valve axle for control flap was leaking oil and loose. (could spin it with my fingers)

 

could this be my problem? or is it something else I need to be checking

Edited by Rgf142

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Sounds like your bike is pretty worn out. Your issues are very typical carburetor related. So I'd go through the carb, clean out the jets, reset the float and see what happens. Yes, reeds need to seal, if you can see past the reeds, they are not sealing. So that will cause the motor to run very strange because with enough pressure on the reeds, I'm sure they seal. With not enough, I'm sure they don't.

The forks just need a re-build, I'm sure the oil is very old. Fork oil should be replaced every 40hrs or every year, whichever comes first. So if the bike is old (which it sounds like it is) then yea... its probably not oil anymore, but something that may resemble molasses. LOL ;)

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As long as your reeds arent chipped or cracked, some light showing through is fine. Even new reeds dont seal perfectly.

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Sounds like your bike is pretty worn out. Your issues are very typical carburetor related. So I'd go through the carb, clean out the jets, reset the float and see what happens. Yes, reeds need to seal, if you can see past the reeds, they are not sealing. So that will cause the motor to run very strange because with enough pressure on the reeds, I'm sure they seal. With not enough, I'm sure they don't.

The forks just need a re-build, I'm sure the oil is very old. Fork oil should be replaced every 40hrs or every year, whichever comes first. So if the bike is old (which it sounds like it is) then yea... its probably not oil anymore, but something that may resemble molasses. LOL ;)

This, The reeds should seal but can work with a small gap, If you can see light replace the pedals (not the whole cage).

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As long as your reeds arent chipped or cracked, some light showing through is fine. Even new reeds dont seal perfectly.

LOL, mine always do. In fact, even after extended use, my Vforce reeds always show no light through. ;)

Yes, you're mechanically correct, just the blowing back of the return stroke is enough to close the reeds if there are slight leak cracks.

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27 years ago I remember the first time my 86 CR 80 wouldn't get on the pipe, was a worn out piston and ring... Agree with the posters here. You just need to spend some time getting it back in shape.

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Alright, thanks guys and yes the bike is a little worn!  so you guys dont think the power valve is bad? I checked the timing and thats fine, could be cleaned,  but thats all I saw.

 

one more problem I found was inside the cylinder wall the sleeve is chipped. what kind of problems can that cause?

Ill probably end up buying the top end kit from LA sleeve, and have a machine shop put the new sleeve in. Has anyone else ever used this kit?

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There are no sleeves on this cylinder, chipped walls (nikasil coating) mean your motor is not going to run properly.

LA sleeves has a top end kit for the 125 with a sleeve ?

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LA sleeves has a top end kit for the 125 with a sleeve ?

Hmm... maybe they used sleeves pre 2003? Thats a good question, I didn't take into account the year of the machine in my answer, sorry about that.

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Sounds like your bike is pretty worn out. Your issues are very typical carburetor related. So I'd go through the carb, clean out the jets, reset the float and see what happens. Yes, reeds need to seal, if you can see past the reeds, they are not sealing. So that will cause the motor to run very strange because with enough pressure on the reeds, I'm sure they seal. With not enough, I'm sure they don't.

The forks just need a re-build, I'm sure the oil is very old. Fork oil should be replaced every 40hrs or every year, whichever comes first. So if the bike is old (which it sounds like it is) then yea... its probably not oil anymore, but something that may resemble molasses. LOL ;)

 

+1 to tye1138's post. Ive had similar problems and after cleaning the carb with a good carb cleaner( cleaning the jets, restting the float level e.t.c. ) it fixed the problem.

Replace the fork oil and seals and that should fix the problem with the forks

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+1 to tye1138's post. Ive had similar problems and after cleaning the carb with a good carb cleaner( cleaning the jets, restting the float level e.t.c. ) it fixed the problem.

Replace the fork oil and seals and that should fix the problem with the forks

My carb is taken apart right now, it looks pretty clean from what I see, the jets are still in there..but when you say resetting the float, how do I do that?

And ill probably just send my suspension off for a rebuild and have it set up for my weight.

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My carb is taken apart right now, it looks pretty clean from what I see, the jets are still in there..but when you say resetting the float, how do I do that?

And ill probably just send my suspension off for a rebuild and have it set up for my weight.

Yea, usually you can't tell how bad the jets are unless you pull them out. So yank'em, soak'em carb cleaner and use a high pressure air line to push out debris. Do a google search for setting float hight and you'll find plenty of video's on the subject. Its very easy to do, but if you haven't done it before, I understand the confusion.

I suggest sending the suspension out as well, somewhere cheap, don't go crazy.

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I bet it's the floats. I had an 03 250sx for a bit and had a very similar issue. Either wet foul the plug, or run like crap down low, only to try to throw you off the seat when the power came on. Not sure what carb you have on the 02 but if my memory is correct the carbs on those models are pretty sensitive. For me it ended up being the needle seat valve was worn/float height was wrong. Once I replaced that and tweaked the height it was fixed. Good luck!

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My 150 had the same problem, slight bogging just as it hit powerband then as the rpms got higher it was fine, I went one notch leaner on the needle and it fixed the problem.. I guessed it was because summer had arrived and it was much much warmer than usual, now winter is on its way I've gone back to original needle position and all seems well, Hope this helps

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Alright so the top end is back on, I cleaned the carb and power valves, adjusted the powervalve and it seems like it has a lot more compression from just moving the kick starter! Just waiting for my new reeds and o rings for the exhaust.

I noticed while in gear, with the bike on the stand the rear tire stays locked up even with the clutch pulled in. Before when it was running it did this but it ran fine, no noises, nothing. Just kept the tire locked up even when rolling down hills with clutch pulled. Shouldn't it be like neutral when I pull the clutch?

I have flushed and bled the clutch fluid and that didn't help, I adjusted my clutch and no luck either.

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