Spark Plug Problems

I have a 2005 KX125 thats been fouling plugs, i've been using NGK BR9ES plugs and this is how it goes: I put a brand new plug in it, starts on first kick, I let it warm up and it runs perfectly. I can cut the bike off and let it sit and crank it back up first kick no problem. Then, I put it up for the night, and the next day when I go to ride it'll start up first kick, run and idle and all, and then bogs down after about 2 minutes and fouls the plug. I can try to clean it but nothing works so i throw a new plug in and the same process repeats.. Anybody have any ideas on why it does this and how to fix it? PLEASE HELP!

Also sometimes on the day after I notice just a tad more smoke than the day before...

Has this problem suddenly come up? Did you buy it like this? Are you loosing tranny fluid? Whats the jetting? How does it ride? Info Info Info....

Has this problem suddenly come up? Did you buy it like this? Are you loosing tranny fluid? Whats the jetting? How does it ride? Info Info Info....

its the mans first post ! give him a break ! start by posting a picture of your plug. what is your fuel/oil mixture? do you have alot of black oily stuff coming out of the exhaust or where it ataches to the exhaust?

Didn't mean to sound harsh, but nonetheless the more info the better. Pics are great too.

Don't know what plug should be in that bike, but a 9 is kinda cold.

I think 9 is pretty common for 125's

When I bought the bike it had a different plug.. didn't pay attention to what it was but the guys at my local shop said the NGK's i'm running should be fine. I always mix 32:1 with high performance mix and premium no-ethanol gas. Yes there is black oily stuff that collects at the end of the silencer.. but i have a shorty and heard that that was common. Also when I pull the plug after it fouls its always black and wet, not dry and dusty.

How does the air filter look?

Clean, I washed it 2 weeks ago

By the way, the stock plug is the NGK R6918B-9, so a "9" is the correct stock heat range.

Is the bike ridden on a MX track, trail ridden or what?

What is your pilot jet number?

Not sure on the jet numbers.. It has an aftermarket Mikuni carb on it and I mostly trail ride, but I stay on the pipe a good bit and I'm not under powering it.

It does not have the stock Mikuni carnuretor?

Oh I guess it does..

If you can answer my questions that would help tremendously.

Sorry, and no I didn't buy it like this it was fine when I bought it but I fouled the original by not letting it warm up. I've only had it for about a month so yes it suddenly came up, no I'm not leaking tranny fluid, I don't know the jetting but the stock Mikuni carb is on it still, and it rides fine, runs, idles, jumps, and stops, like it should.. No throttle studdering or anything

It is jetting be best to get a Kawasaki repair manual around $35 dig into that carb and find out what jets are in it. Disassemble clean and re-jet "leaner" and replace that packing in the silencer also. I'd also run a compression test to make sure the motor is ok, low compression can make it go fat.

Edited by JBFL

Thanks! Ill get a manual and see what I can do

Team Green suggests going one leaner on the pilot and main.

Are you familiar with the air screw?

I believe so.. It's the screw on the left side of the carb with a Philips head right?

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