Kawasaki KX125

[fazer]

My son and his friend have both bought a kawasaki kx125 (2008). His friends bike however has developed a problem. When it starts it regularly bogs out, struggles to tick over, and it burns out 2 spark plugs per event we attend. plugs are always clogged up with oil when removed, although it runs ok. I am stumped at the possible problem. Has anyone had the same problem or know of a cure? Thanks

[scott411]

what type of fuel and oil mix are you running?

also what are the main and pilot jet sizes?

and what sort of plugs are you putting in it?

[LittleJohn]

I would start by pulling the carb to bits and cleaning and checking the jetting. Also check the Reeds.

[vr4king]

X3 on your jetting maybe check and record the jetting on the good one and copy it to the bad one including needle clip position

Pre-mix on a 125 should be around 30:1 with good oil..........the more oil you add the leaner it runs but lets not get into that arguement

Also dont count out the electrics ie coil etc

[scott411]

X3 on your jetting maybe check and record the jetting on the good one and copy it to the bad one including needle clip position

Pre-mix on a 125 should be around 30:1 with good oil..........the more oil you add the leaner it runs but lets not get into that arguement

Also dont count out the electrics ie coil etc

i disagree on that, if it is not being ridden hard 40:1 is a better mix in my experience, race bikes should be on 30:1 or close but i know it causes oil fouling issues if it is not being burnt off,

[morg_nz]

well i checked everything on my cr125 from the time i bought it - it was running like crap, no bottom end but fine top end. did everything to the carb, and no change. pulled the cylinder out and found that he idiot previous owner had bored out the exhaust port so it was getting no compression at low rpm's (i.e. the exhaust was flowing out over the powervalve before the pison had got past the bottom of the powervalve.

i'd pull teh cylinder and head off - it wont take much more time and would save you hours trying to get the carb right if its that! (it cost me a new cylinder though lol!)

[vr4king]

i disagree on that, if it is not being ridden hard 40:1 is a better mix in my experience, race bikes should be on 30:1 or close but i know it causes oil fouling issues if it is not being burnt off,

You are right there too if its not ridden hard yes 40:1 is ok and some oils can cause issues

[Reckless]

ok Firstly I wouldn't be pulling a barrel off till you have eliminated the simple things!

Are the jets at least close between both bikes that's a simple first up check.

Give Scott your jets sizes for a reference check he knows what he's doing!

If I where to pick one thing to look at over all the other things it could be I'd check the choke circuit and then float valve and/or float level if you find the jets are within an acceptable range?

[Crasherfromwayback]

Is the air filter nice and clean?

[CHOPPA]

You should run it on ams oil 100-1 hahaha

[morg_nz]

ok Firstly I wouldn't be pulling a barrel off till you have eliminated the simple things!

Are the jets at least close between both bikes that's a simple first up check.

Give Scott your jets sizes for a reference check he knows what he's doing!

If I where to pick one thing to look at over all the other things it could be I'd check the choke circuit and then float valve and/or float level if you find the jets are within an acceptable range?

i contend - carbs can be very fickle, and for the amount of time it takes to get a carb out and apart you can also get a barrel of a 2 stroke off (takes me about 20 - 30min to get it off). you have a lot of variables with the carb but less with the cylinder. i just think it is worth a look to save you potentially a lot of hours on the carb?

[Ride it till the red]

i contend - carbs can be very fickle, and for the amount of time it takes to get a carb out and apart you can also get a barrel of a 2 stroke off (takes me about 20 - 30min to get it off). you have a lot of variables with the carb but less with the cylinder. i just think it is worth a look to save you potentially a lot of hours on the carb?

Your bike is rather old and as such is much more likely to have been butchered along the way like you found. The chances of something being wrong with the cylinder in an 08 bike are much less than the chances of something being slightly wrong in the carb. Plus, who wants to buy gaskets for no reason?

As above, it sounds like carb issues to me. As Reckless (I think) said it could easily be on the choke circuit. If your methodical the carb should be relatively simple to look over, especially as you have an identical one thats working well to compare it to....

And it may sound silly but you might want to check he knows how to mix the oil and fuel properly. A couple guys I know thought 40:1 meant 40 mls of oil to 1 litre of gas..... After having ridden for a couple years :facepalm:

[cambocambo]

I will be interested in what you find, we tend to go through a spark plug per ride, which is a piss off, also on a kx125 (2000)

I think that we have been oil fouling them, we were mixing oil at 35:1 but have dropped back to 40:1 and rebuilt and cleaned the carb. it seems to have improved.

[fazer]

Thanks for all your replies, guess it aint so straightforward as I might have thought. Done all the apparent simple things, fuel ratio (just checked that we had got it right!), air cleaner etc. Looks like a trip to someone who is a bit more knowledgeable than myself! Will post any findings for future reference.