fouling plugs like crazy

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#1
i have a 95 kx 125 and lately i have been fouling out plugs like they are goin out of style. i know that it is easy to foul a plug on a 2 stroke, but when you are riding it hard i don't think they should foul almost every 2 hours of riding, probably less than that. i talked to some guys i ride with and they said i should put in new piston rings, so i ordered a new piston ring and gasket set, but do you guys think this will fix the problem.

(also i have a post about how to put in the piston rings because i have never done it on my own, it'd be great if you guys would go and read it and give me some hints, it is called HELP PUTTING IN PISTON RINGS?)
 
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#2
Replace the right side crankcase seal before you install the new piston. That is the most likely culprit for an engine that fouls plugs regularly. Crankcase oil in the cylinder can potentially damage the piston (not severe but it wears a groove in the piston over the exhaust bridge), but it's best to replace the seal before putting a new piston in.
 
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#4
You need a new piston. Do you even know how many hours are on the current one? 20-30 hours is getting toward the worn out end of a piston's life. Your bike probably needs a new top end, but worn rings don't cause plug fouling. You'll need to repair the cause of the fouling as well.
 
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#5
20-30 hours is getting toward the worn out end of a piston's life. I do not know where this information came from. First thing you need is a manual! In my opinion,the average life of a piston on a 125 should be 10 to 15 hours,some are less! Most of the time a blown crankseal happened because the main bearings/big end of the rod are shot. Gm,care to take a stab at the recommended crank life?
 
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#6
try this

your mixture of gas to oil might be a little off. Ride your bike with a new plug for about 30 minutes and check the plug. If it is Black then you are running TOO much oil. If the plug is LIGHT BROWN the you are running the PEFERECT mixture and anything lighter than that you are running TOO much gas. Keep checking your plug, its the sign of mixture!
 

sick 96 250

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#7
Never heard 10-15hrs being the life of a piston/rings. So I don't know where you are getting that info from but that is crazy. So after 2 normal days of riding half my buddies should be replacing there top ends? Its all about maintaining your bike and having it dialed in. My RM250 has well over 60hrs on the top end and its still pumping over 210psi and running like a raped ape. My buddies RM125 prob over 80hrs and going strong as well. Maybe racers need to do that but the AVG rider I dont see that being normal.

With that said, yes it could be a top end is needed but my buddy had something very similar to this with his 95 RM125. He would ride the bike for about an hour or so and it would foul plugs and be blowing lots of smoke. The bike ran pretty good though between fouls. We put a new top end in, replaced right side seal and still the same issue. After pulling everything apart a couple times the culprit ended up being the carb. The floats were way out of whack in which was messing with how fuel was being delivered causing all the aggravation. So check your carb!! There were many people with us riding when this was going on and almost all said it was the right side seal, even though we replaced that anyhow, we could of saved ourselves a lot of time.

What is your jetting at "main, pilot, air acrew, needle clip"? What temps/humidity and elevation are you riding at as well.
 
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#8
Since when did they start giving trophies for the most neglected 2 stroke race bike? You are seemingly up on that! An owners manual,if you ever seen one makes no distinction on how the person intends on using this mx race bike. 02 Cr 125,recommends piston And ring after like 7.5 hours,yes,for making sure you do not frag the motor and cuss everybody who has ever lived for building a 2 stroke race bike,yes. And the cr,I put the wiseco in it and the ring goes every 4 hours,piston every other ring. If I were going to need a dirtbike to ride all day it would NOT be a mx bike,maybe,I do not know,how about an enduro model! If you ever plan on racing mx professionally,I would get a mechanic,they rebuild them a lot more than the soft factory recommendations! A 250 lasts about twice as long. Nobody going to take even a wild guess on how long the crank SAFELY lasts on a 125 racebike?
 

sick 96 250

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#9
No need to guess if you know the answer exactly already. I'm going to change out my top end now since I past the mark by 40hrs or so. Thanx for the pissing match, you put me in my place.
 
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#10
It is not like that,at all. It has to do with what you were taught,listen to. Mis-information is cheaper,less work and way more abundant! My goal is to attempt not perpetuating this no where path. I seen Dr. Blair has been back by,I miss Eric and Jeremy,the perpetrators do not like these men,go figure! There is no doubt in my mind that not pushing these racebikes,not riding them like you stole them,can greatly prolong their maintenance schedules. But no way would I endorse someone else to do this! When they get intelligent enough to apply what and how their schedule can be milked out to,without catastrophic failure. To a racer this can mean death or injury,not to mention rebuilds into 4 stroke prices!
 
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#11
I don't know, what is the life of a crank? It isn't listed in the service manual so it must not have one.
 
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#12
i have a 04 kx 125 and it eats plugs like crazy, so i changed mixture from 32:1 to 42:1, and it allowd me to go a couple days with out fouling, but then it recently ate 2 brand new br8eg's.. so im on the same page.
 
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#13
yzpowerband said:
i have a 04 kx 125 and it eats plugs like crazy, so i changed mixture from 32:1 to 42:1, and it allowd me to go a couple days with out fouling, but then it recently ate 2 brand new br8eg's.. so im on the same page.
Yes and when that seal gets bad enough it will either tell you its time and implode in a million pieces,potential repair bill around 1500 for parts,if available. Or by keep dropping the oil ratio ignorantly you wikk be running straight gas and tranny fluid,smells bad,potential parts estimate at 320 dollars. Umm,what to do?
 
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#14
well i just got the parts in for my bike so i am going to replace the seal, but it sounds like i will have to check the carb because i have never messed with it really, or checked it
 
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#15
also is their a place online where i can just look at a service manual online without buying one??