03 KX125 start-up issues

[zachjk]

I just picked up an 03 kx125 the other day. Went to fire it up this afternoon, and it did that, but bogged out. I try to start it up, and nothing. I have since been trying, with periods of rest in between to keep from flooding the engine, for the past hour or two. I've removed the air filter, and cleaned it. I've cleaned out the carb. I've checked for spark. I've done just about everything i can think of, short of checking compression and changing the fuel. It doesnt seem to be either seeing as I've driven it two seperate days without any problems other than a fairly typical slow cold start-up. Does anyone have any ideas here??
Thanks...

I just found out that the bike is jetted to run up high. Me not keeping the revs up probably fouled the plug. I wish i knew this when I got the bike. How do I change this so that it will be back to normal?

 

[mmz77]

...Sounds to me like your jetting is off, I would check your spark plug for color and go from there. If everything else you stated was correct then this would be the next area I would examine... :cool:

 

[IndyMX]

Try a brand new plug.. Could be that the one you have shows spark, but that the spark is too weak to fire the engine.

Never assume that just because you see spark that the plug is good.

 

[zachjk]

I just tried a different plug from another 125 I had laying around. Absolutely nothing. I took out the plug, opened the throttle and cranked it over to try and clear out any excess gas, just incase it was flooding. Still nothing. The other plug I tried should be fine.

 

[IndyMX]

Again, make sure you have a new plug.. Not one that "should be fine".

Check the float level in your carb.

If you have Spark, Fuel, Air and Compression, you have to have fire.. It only takes one of those removed from the equation to keep it from running.

 

[IndyMX]

...Sounds to me like your jetting is off, I would check your spark plug for color and go from there. If everything else you stated was correct then this would be the next area I would examine... :cool:

If the bike won't run, it's nearly impossible to "check your spark plug for color". Whatever color he see's won't be accurate.

Once the bike is running, you can check jetting...

 

[zachjk]

What plug would be best for this bike. I'm fairly new to bike's, so I'm not really sure where to get the plug or what type for a two stroke. My knowledge is mostly limited to things with 4 wheels right now. I'm gonna check compression as well. It is only supposed to have like 15 hours on a new top end so it will hopefully read somewhere around 145.

 

[IndyMX]

You should be ok with a BR9ES

 

[zachjk]

Okay, thanks. I'll give that a try in a little while.

 

[zachjk]

I just found out that the bike is jetted to run up high. Me not keeping the revs up probably fouled the plug. I wish i knew this when I got the bike. How do I change this so that it will be back to normal?

 

[kx125412]

I would go with a BR8ES since he is running rich from what he says. Same thing happened to my brothers bike a week ago the bike started up stuttered and died. Plug still appeared to spark fine, went through everything else and still nothing. Finally went in got a new plug and what do you know, it runs. It's still jetted rich i'll have to take care of that later on.

Also, do you have any previous experiance with bikes? After riding for awhile you can tell where the bike is rich or lean by the feel and sound mostly. Does you bike smoke lots on start up and kind of boggy in the mid range? I would get a leaner pilot and drop your needle a clip or two and it should clean it up a bit.

 

[IndyMX]

I just found out that the bike is jetted to run up high. Me not keeping the revs up probably fouled the plug. I wish i knew this when I got the bike. How do I change this so that it will be back to normal?

It's a 2 stroke.. They all are designed to run high revs..

Best bet is to get it running how it is now, then take it out and do a throttle chop on it...

do a search on Jetting on here, there is a thread in the KDX forum about jetting that is pretty good.. will give you all the info you will need to know about getting your bike jetted properly.

 

[zachjk]

It's a 2 stroke.. They all are designed to run high revs..

Best bet is to get it running how it is now, then take it out and do a throttle chop on it...

do a search on Jetting on here, there is a thread in the KDX forum about jetting that is pretty good.. will give you all the info you will need to know about getting your bike jetted properly.

I found that jetting article last night. I will be working on getting the jetting to as close to normal asap. A new plug did work though, so that was nice to see. Thanks for all the help....

 

[KX250Dad]

Should the outdoor temps be cold 30degF or lower use the choke and as hard as it will be for you DO NOT THROTTLE with the choke on/up. When cold you might consider having two plugs handy... one to get the bike to fire with the choke up and when it boggs/dies... change the plug and I suspect you will be good to go. Experienced this with both the YZ125 and YZ250 somewhat recently.

In so far as the jetting thing... if your new to the 2 stroke get the manual. You need to know your jet #'s and clip position to know where your at now and compare these values to the book... never listen to anyone, know for fact. I generally suggest starting with factory jetting/clip position and go from there.

Being cold... be absolutely sure the bike is at least warm prior going under load.

It's simple, get the manual and the rest will make more sense to you.