i have a kx 125 and i keep fouling out plugs we ran a hotter plug fould out in 30 min when we take it out the part thats in the header is liquidy and pitch black we treid running my fuel mixture 50:1 still doing same thing we get a lot of smoke at the begging and alot of blow buy at the bottom on surtain days it will run fine but when i shut it off it wont start unless i put a new plug in it
Problems
- Thread starter xxKX125xx
- Start date
Seems like you have been dancing all around the problem.
Jetting.
If you don't jet right, you will never get it running right.
You're bike is way too rich, you need to buy some jets, and read about jetting.
It's not really that hard to do.
Jetting.
If you don't jet right, you will never get it running right.
You're bike is way too rich, you need to buy some jets, and read about jetting.
It's not really that hard to do.
If you are running rich, then change the oil ratio from 32 or 40:1 to 50 to one, then you will only run richer. Realistically evaluate your riding style, if you are truly on the gas and WOT all the time, then run the factory recommended plug. I feel like I am riding hard at times, but the reality is I cannot use an 8 heat range because I don't work my 250 smoker that hard. The 8 plug will last 2 weeks, a 7 stays in place for at least a year. After that, JET THE BIKE. If it is not right, then nothing else matters. Pull the carb, clean it, baseline it with stock parts, and adjust from there.
rmc_olderthandirt
~SPONSOR~
- Apr 18, 2006
- 1,533
- 8
I have a '97 WR250 (two stroke) that I had the same problem with, it would foul plugs left and right. I learned early on to never venture far from camp unless I carried a spare plug and a wrench to change it.
When I got the bike it had a BR8ES plug in it. I changed to a BR7ES, which helped a little. If I was pushing it hard, like when I rode an enduro, it would be fine. When I went for a putt putt ride with the wife I would be lucky to make it 10 miles.
I put up with this for two years and finally decided to get serious about it. Due to the age of my bike I couldn't just buy a "JD" kit and going to the leanest jets the dealer offered didn't help. Then I found online places that sell jets for carburetors. Not for a bike, for the carburetor.
What surprised me the most is how much I changed it before there was any significant difference. I ended up 6 sizes smaller on the needle jet and 4 sizes smaller on the main, and I may still drop the main one size smaller.
I also started running a BR6ES plug.
Finally, things are looking better. Before I would be changing plugs several times on a weekend. After my last weekend outing, with a total of perhaps 8 hours of riding time I took the plug out, inspected it, and put the same plug back in! It wasn't perfect, but at least it wasn't black and sooty and ready to foul.
Rod
When I got the bike it had a BR8ES plug in it. I changed to a BR7ES, which helped a little. If I was pushing it hard, like when I rode an enduro, it would be fine. When I went for a putt putt ride with the wife I would be lucky to make it 10 miles.
I put up with this for two years and finally decided to get serious about it. Due to the age of my bike I couldn't just buy a "JD" kit and going to the leanest jets the dealer offered didn't help. Then I found online places that sell jets for carburetors. Not for a bike, for the carburetor.
What surprised me the most is how much I changed it before there was any significant difference. I ended up 6 sizes smaller on the needle jet and 4 sizes smaller on the main, and I may still drop the main one size smaller.
I also started running a BR6ES plug.
Finally, things are looking better. Before I would be changing plugs several times on a weekend. After my last weekend outing, with a total of perhaps 8 hours of riding time I took the plug out, inspected it, and put the same plug back in! It wasn't perfect, but at least it wasn't black and sooty and ready to foul.
Rod
longtime coming
Member
- Mar 18, 2006
- 265
- 0
And some bikes/carbs are sensitive to small changes.
First off, is everything in good condition?
How many hours on the top end?
Reeds in good shape? Not chipped or frayed, and closing fully?
Using any transmission oil (crank seal leak)?
If everything above is good, it's time to look at the carb.
Float height set properly?
What size jets are in it?
What size jets come stock?
What modifications have been done to the bike? Pipe? Silencer? Spark arrestor? Big bore? Porting? Etc etc....
How many hours on the top end?
Reeds in good shape? Not chipped or frayed, and closing fully?
Using any transmission oil (crank seal leak)?
If everything above is good, it's time to look at the carb.
Float height set properly?
What size jets are in it?
What size jets come stock?
What modifications have been done to the bike? Pipe? Silencer? Spark arrestor? Big bore? Porting? Etc etc....