Porstala F9

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Jul 30, 2003
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Hey guys, I was recently suprised this morning when my father was standing there with a brand new, beautiful KX 125 for a christmas gift :)

Its a 2003 KX 125 that he got a great deal on a leftover model..

Anywany.. I have a couple questions regarding this bike..

First off, what spark plug would you reccomend me to use with this bike for beginner on this bike, coming off an XR 80 which I can ride fairly agressivly. I am mainly going to be using the low-mid end power of this bike a lot, and the guy who delivered the bike to me gave me a quick run thru on the bike, and said that the kind of speed riding you are going has a great effect on the spark plug and the amount of time and performance you will get from it. Its got an NGK BR9EIX now, which is what it came with. I am going to the dealer on Friday to pick up all my new gear, gas, oil, etc and things, so what type of spark plugs do you reccomend for me to buy?

And also, I was reading the manual when I came accross the information about the "Break In" period info. What they reccomend to do is for the first hour or so do as follows: Ride the bike for 10 minutes and then let it cool, at a moderate speed and never accelerate hard (which I can understand) - They then say to then ride again for 20 minutes and again, at a moderate speed and avoid accelerating hard. After this they say to stop the bike and let it cool and then drain all the coolant, inspect the cylinder head, cylinder, and piston and then reinstall them and fill up the coolant in the radiator.. they also reccomend replacing the piston rings after break in.. and then ride it again for 20 mins and then change the plug and its broekn in.

Is the dissasembily of the engine part REALLY nessicary? It seems a bit conservative and a bit much to me, but maybe its just because I am new to this stuff. How much of an effect will this have. I don't think I am prepared to dissasemble the engine, since I hardly know anything about these engines. If I follow the steps about riding the bike at moderate speeds without accelerating hard, in the time periods they give me, will I be good, or is it really nessicary to dissasemble the engine, and then after break in period, change the piston rings.

Any information would be greatly appriciated. Any info on this, opinions, suggestions, or any advice relating to the issues I stated, or any advice with the bike are GREATLY appriciated.

Thank you, and Merry Christmas and Happy Holidays everyone!! :)
 

hoosierf

LIFETIME SPONSOR
May 6, 2001
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Search Marcus Gunby's posts for information on the plug. He has posted some good information on that topic. I don't know anyone who tears the engine apart after break in.
 

Porstala F9

Member
Jul 30, 2003
345
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Originally posted by hoosierf
Search Marcus Gunby's posts for information on the plug. He has posted some good information on that topic. I don't know anyone who tears the engine apart after break in.

Thanks for the reply :)

I can't search since I am not a subscirber. But I did a look at threads and the only thing I came accross was this:

http://www.dirtrider.net/forums3/showthread.php?s=&threadid=67116

Any other advice? Thanks! :)
 

marcusgunby

LIFETIME SPONSOR
Jan 9, 2000
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The 04 comes with a more durable plug i would use that one, i dont dissassemble the bike after break in, just run it in as per manual with the 04 plug and it should be a great bike.I had to lean the jetting slightly on mine, i went to a 35 pilot AS1.5 and a 400 main.
 

NEMX305

~SPONSOR~
Mar 25, 2001
106
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When you regrease the linkage, and swingarm bearings, make sure you completely seat the seals. I was surprised with my 04 250, that if those seals ( on the linkage) are not completely seated, there is a ridge on the spacers(thrust washers?), that will cause the linkage to have alot of resistance while moving the swingarm through its stroke.
 

Porstala F9

Member
Jul 30, 2003
345
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Thanks for the replys guys!

So what is the model of the plug you are reccomending me? Looks like right before I was done breaking it in, the plug fouled. Everyone around here says this is normal, and I reffered to the manual, and sure enough it says that with the new bike, and the plug that they give you, there is only about 30 minutes, so that reassured me :)

Allright, thanks for the replys guys, and keep em' coming. I'm going down to the dealer tomorow, so I need to know exactly what plugs to run. Its not that 22$ RM 125 plug, is it? :(

thanks! :)
 

marcusgunby

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Jan 9, 2000
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i dont think its identical to the rm plug but its very similar, just ask the dealer to look up the 04 KX125 std plug.It maybe more expensive than a BR9eix but its sure cheaper than a engine rebuild.Many of the std ones broke in 03 and left many riders with a damadged engine.Kwak replaced the plug for 04 for a reason.
 

Porstala F9

Member
Jul 30, 2003
345
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Originally posted by marcusgunby
i dont think its identical to the rm plug but its very similar, just ask the dealer to look up the 04 KX125 std plug.It maybe more expensive than a BR9eix but its sure cheaper than a engine rebuild.Many of the std ones broke in 03 and left many riders with a damadged engine.Kwak replaced the plug for 04 for a reason.

Allright thanks man. I'm a beginner to this bike, so I might be fouling plugs a lot, so is a more expensive plug really the way to go? I'm going down to the dealer tomorow, so I will probably buy one of those and I would also like to buy a few other spark plugs that are cheaper, besides the standard BR9IEX plugs? I wanted to also experiment to see which of a hotter or a colder plug would suit me best. So should I go and buy a couple of plugs and experiment and see which one suits me best? Or am I taking a risk by putting in any spark plug other than the ones that the 04's are standard with? Or only taking a real risk with the IEX plug?

And also, two quick things - 1) After about 25-30 minutes of breaking it in riding it around the yard and around in moderate speeds, the spark plug seems like it fouled. I reffered to the manual, and it says that it is likely that it will foul within about a half hour while breaking it in at low speeds with carbon fiber build up. This is normal, correct? and 2) I also saw a significant amount of "spooge" coming out of the silencer and dripping down it. Is this something I should worry about, or is this because the bike is new?

Thanks again in advance, and excuse my newbishness here! :)
 

bclapham

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Nov 5, 2001
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if the plug is fouling, that is becasue of the carb setting and not the plug. go to the dealer, get the 04kx plug and then get some jets as well. then have a look at www.eric-gorr.com for a jetting guide
 

Porstala F9

Member
Jul 30, 2003
345
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Originally posted by bclapham
if the plug is fouling, that is becasue of the carb setting and not the plug. go to the dealer, get the 04kx plug and then get some jets as well. then have a look at www.eric-gorr.com for a jetting guide

I just got the bike brand new, and after 25 minutes of riding I allready need to rejet it?! Oh man.. :(

Allright, thanks guys.
 

holeshot

Crazy Russian
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Jan 25, 2000
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Most 125's come jetted rich when new - it's been the same for the past 30+ years . I suppose the manufacturers would rather err to the rich side in order to cover their arse.
I use the spark plug from an '03 RM125 (works fine), but I'll probably use the the plug from an '04 KX125 when it's time to replace it. The original '03 KX plug didn't fail on me, I just replaced it for cheap insurance.
Other than that, the KX125 isn't any different than any other bike (check spokes and fasteners). Just ride it like you stole it.
 
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Porstala F9

Member
Jul 30, 2003
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Thanks :)

I was at the dealer today and asked about the 04 plug, and he said that I should start out with 6 "BR8ES" plugs, and he said that since I am new at the bike, I should blow through a couple of these cheap plugs while learning and breaking in the bike, instead of taking the chance of blowing more expensive plugs in this period of learning. So was this good advice that he gave to me or a good decision on my part? I figured that it must have been if he wasn't pushing me into buying the more expensive plug ;)

I allready went to thru another plug and lent my friend one, so I am down to the one in the bike now, and three others. The one plug fouled almost instantly. Maybe I didn't warm it up enough, because I noticed when I tried to get on the throttle, it sounded like it was deffinetly hesitating to even get into the powerband, so I let off the throttle a bit, so the plug fouled in about 8 minutes of slower riding. I know this was bad, and I deffinetly learned from my lesson, so should I deffinetly warm it up a lot more? I was afraid to really rev the bike too much when idling and warming it up when I first start it, because the guy who delivered it said not to. But the guy didn't seem to know much about bikes.

Thanks again guys, you are all a great help for a new rider. I'll try to ride it as hard as I can after warming it up! :)
 

bclapham

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Nov 5, 2001
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go back to the dealer and ask him to give you some jets, the bike needs help there, you treat the problem and not the sypmtom- if you are upset that the bike is new and you have to re jet it, then get over it- jetting can change from track to track, day to day and rider to rider- the specs marcus gave above should be a good starting point. if you are new to bikes, go to the local book store and get the book by Eric Gorr- jetting techniques and all other maintainance is in there.
 

marcusgunby

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Jan 9, 2000
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If you dont get it jetted right, you will spend more on plugs than i do in tyres.Once jetted right it should never foul a plug again.I had a cheap plug in when my engine blew, this was a combination of detonation and a cheap plug.Dont make the same mistake i did.
 

Porstala F9

Member
Jul 30, 2003
345
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Originally posted by marcusgunby
If you dont get it jetted right, you will spend more on plugs than i do in tyres.Once jetted right it should never foul a plug again.I had a cheap plug in when my engine blew, this was a combination of detonation and a cheap plug.Dont make the same mistake i did.

Never foul a plug again, that sounds good! Even when not riding hard? :)

I talked to my father about the jetting, and he said that he knows about carbs since he used to have a couple 2-strokes back in his day, and he says he should be able to help me. Should I jet right away, or maybe wait about a month or so to jet?

And again, thanks for the replys!
 

23jayhawk

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Apr 30, 2002
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Read the Eric Gorr guide that Marcus referenced, and learn to do basic jetting. It's really not that difficult, though it might seem intimidating at first. Once you have some basic understanding you will be able to get almost any bike into rideable condition.

 Buying a 6-pack of plugs is not a solution, and I'd question the guidance of any dealer that leads you in that direction rather than take the time to give you some basic information on jetting.
 

marcusgunby

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Jan 9, 2000
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Do the jetting now as its just wasting time to keep replacing plugs, once jetted it may still not like riding slow for extended periods, but all you need to do is 'clear it out' every so often, this involves just riding it wide open for a few seconds so burn off oil deposits on the plug.Even holding the clutch in and giving it a good rev once every 10 minutes will help. If you use the jetting i suggested, it will ride well for a good few minutes at low speed without fouling a plug.If you then take the time to clear it out after 10 minutes of slow riding, it will last for probably 6 months on the 04 plug kawasaki reccomend.
 

Porstala F9

Member
Jul 30, 2003
345
0
Ok, thanks a lot.

I will buy a jet kit as soon as possible and try those settings. Thanks!

btw, today I took it out and really broke it in. Man does this thing have power! I rode for about 25 minutes with a fresh plug, and then let it cool and took a break, and then took it again for around 10 mins and then I stopped it, and then after this, it fouled when I tried to start it up again. This was with the BR8ES which I am told is a plug designed for hotter weather, is this true? It is only 50 degrees out, so maybe that is a contributing factor?

But anyway, I'll try to pick up the 04 plug. Does anyone know what the exact model is on the 04 KX 125 spark plug? Thanks again guys, you guys rock.
 

Porstala F9

Member
Jul 30, 2003
345
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I don’t know if I would jump right ahead and buy a jet kit so quickly. My advice would be to give it some time. With my 03' KX 125 I was fouling plugs a lot, and I too had a bit of spooging occurring when I first got it as well. After I got a couple hours on it, and broke the bike in more, the fouling of plugs problem was occurring much less. My average plug after that lasted almost 2 and sometimes 3 months, even with some slow paced trail riding, all with stock jetting. I recently rejetted the bike and I am now on the same spark plug I was on in August and it has yet to foul :) *knock on wood*

But if the problem persists, I would also recommend jetting. But give it a few hours first.
 

holeshot

Crazy Russian
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Jan 25, 2000
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Originally posted by Porstala F9
I don’t know if I would jump right ahead and buy a jet kit so quickly. My advice would be to give it some time. With my 03' KX 125 I was fouling plugs a lot, and I too had a bit of spooging occurring when I first got it as well. After I got a couple hours on it, and broke the bike in more, the fouling of plugs problem was occurring much less. My average plug after that lasted almost 2 and sometimes 3 months, even with some slow paced trail riding, all with stock jetting. I recently rejetted the bike and I am now on the same spark plug I was on in August and it has yet to foul :) *knock on wood*

But if the problem persists, I would also recommend jetting. But give it a few hours first.


You're making this jetting thing sound like VooDoo or some sort of black art to be feared. It only takes a few minutes to swap to leaner jets. I've gone all the way down to a 130 on the pilot (but most only went down to a 35 or 37.5). I don't know what this "kit" is - the jets are individually available at nearly all dealers that sell japanese bikes.

Your saying that your bikes was really rich at first, but after a few hours it lean out? I've got some beach front property in Arizona that you might be interested in. Just because you haven't fouled a plug recently doesn't mean it's jetted right. (You are way too rich)
 

Porstala F9

Member
Jul 30, 2003
345
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Originally posted by holeshot



You're making this jetting thing sound like VooDoo or some sort of black art to be feared. It only takes a few minutes to swap to leaner jets. I've gone all the way down to a 130 on the pilot (but most only went down to a 35 or 37.5). I don't know what this "kit" is - the jets are individually available at nearly all dealers that sell japanese bikes.

Your saying that your bikes was really rich at first, but after a few hours it lean out? I've got some beach front property in Arizona that you might be interested in. Just because you haven't fouled a plug recently doesn't mean it's jetted right. (You are way too rich)

Sorry if my post was a bit misleading, but I am not saying that the bike does not need jetting help, but I remember when I first got my 03 KX 125 and the situation he described seemed very similiar to mine. It fouled tons of plugs within the first week or so, and then didn't foul nearly as frequent. So I suggested him to give it some time, and then if the problem persists, to then get into the jetting.
 
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