Some Quick KX-125 Questions!

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#1
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

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#2
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.
 
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#3
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

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#5
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

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#6
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.
 
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#7
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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#8
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.
 
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#9
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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#10
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
 
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#11
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

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#12
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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#13
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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#14
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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#15
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.