KDX fouling sparkplugs

[antferny]

Late last year I brout a 91 kdx250 it had done 11 hours riding after a full rebuild , I have since done 8 hours riding and Ive just fitted a 2nd new sparkplug , this is my 1st 2 stroke but Im pretty sure that I should be getting more then 4 hours out of a plug???? am i running it to rich? I do cruise on it a bit could this be my problem also The previous owner was mixing it 35:1 and told me that I dont have to go balls out all the time on this bike, any help much appreciated

[Rupe]

Late last year I brout a 91 kdx250 it had done 11 hours riding after a full rebuild , I have since done 8 hours riding and Ive just fitted a 2nd new sparkplug , this is my 1st 2 stroke but Im pretty sure that I should be getting more then 4 hours out of a plug???? am i running it to rich? I do cruise on it a bit could this be my problem also The previous owner was mixing it 35:1 and told me that I dont have to go balls out all the time on this bike, any help much appreciated

I'm pretty sure they should be 32:1 but 35:1 is prob fine. It's worth pointing out that when people talk about rich or lean jetting it's the air/fuel ratio, NOT the amount of oil you are mixing.

There are heaps of threads on jetting plugs etc on here if you seach, but you could be on the money if you're crusing too much, try a lower gear its not a tractor!

[tommorth]

should be able to tractor all day withthe correct jetting I have only fouled one plug on my 200 and that was with excessivly rich jetting

choose a fuel oil ratio you like then jet the bike to it . There are hundreds of in depth threads on the net about how to jet your bike even a couple of good one on here

[krad_nz]

I have a 2006 KDX200 and found myself fouling plugs on occation. I run 40:1. In the end I dropped the needle one notch and its never fouled a plug since.

I should probably change it back to standard now that I'm riding it bit more aggressively.

[theblacksmith]

I run my kdx 250 on 32:1.
The only time I ever fouled a plug was when I used Maxxol Racing Castor Oil. And this happened 2.5kms into the bush at the Neavesvilles which turned out to be a mission. Ive not used that oil since and plugs will do 40-50 hrs.

[Rmxer]

What heat range plug are you using?

im had a 92KDX200 back in the day and when i bought it fouled plugs everytime i rode it

threw a hotter plug in and it was fine.

For the slower stuff you will need a hotter plug so it can clear itself, once you get faster and ride faster tracks you could consider throwing the colder one back in

[Reckless]

A plug should last you a year mate. Best place to start is stock. Take the carb to bits incl removing the pilot jet. Check everything against stock.
Best advice I can give over the net other wise its pretty much a hands on thing!

I hate giving tuning advise over the net but going to 40:1 and or dropping the needle one notch (only do one at a time) shouldn't hurt if its already rich enough to foul plugs every 4 hours.
but if its your pilot thats too large your feeding fuel right through the range with it even off throttle which may be why its fouling.
Can't tell without looking at the plug.

O shit the above is to risky on a new engine that I can't see!
I go back to my first line, check everything against stock Needle size, Main jet, pilot jet, Float level, float valve for seal!! Clean everything!!
Check the heat range of your plug against stock as well.
Let us know!

Good luck!

Oh one more thing. Been anywhere muddy? make sure the dump tubes are not blocked with mud where they hang down (or kinked or cable tied to tight) this can often be a to rich symptom when the carb can't breath!!

[Danger]

Yes you are running too rich if you are fouling plugs.
Be aware that if you change from 35:1 to 40:1 it will run even richer.

[evoetr]

Late last year I brout a 91 kdx250 it had done 11 hours riding after a full rebuild , I have since done 8 hours riding and Ive just fitted a 2nd new sparkplug , this is my 1st 2 stroke but Im pretty sure that I should be getting more then 4 hours out of a plug???? am i running it to rich? I do cruise on it a bit could this be my problem also The previous owner was mixing it 35:1 and told me that I dont have to go balls out all the time on this bike, any help much appreciated

Rev the sh!t out of it more, also when you have finished riding turn the fuel off and blat around the carpark until it runs out of petrol in the carb. You should do that every ride, also if you are going to start the bike for a short time and stop you will need to rev the nuts off it to burn that excess oil. Even if you ride like a nana just stop like halfway on your trip and rev the crap out of it then keep going ...... dont be shy on the rev

[Danger]

Please tell us your not being serious.

[evoetr]

Please tell us your not being serious.

Yea, got that out of a motorcycle mag about turning the fuel off and running the carb empty works a treat!

2 Strokes arn't nana bikes, you got to give them beams! my mates Kawasaki fould up when he first started out but as he got better at riding and rev'd it higher it stopped fouling up we also ran the fuel and oil mix 32:1.

We didn't have to change the plug for a whole 4-6 months....

But yea the jet's would need to be adjusted to your style of riding if you continue to cruise.. or lower the oil ratio... are you running the correct plug ?

Also we had problems with cheap 2 stroke oil, considering how far a 1 ltr of oil will go its worth getting the top of the line oil...

CB

[Rupe]

Yea, got that out of a motorcycle mag about turning the fuel off and running the carb empty works a treat!

2 Strokes arn't nana bikes, you got to give them beams! my mates Kawasaki fould up when he first started out but as he got better at riding and rev'd it higher it stopped fouling up we also ran the fuel and oil mix 32:1.

We didn't have to change the plug for a whole 4-6 months....

But yea the jet's would need to be adjusted to your style of riding if you continue to cruise.. or lower the oil ratio... are you running the correct plug ?

Also we had problems with cheap 2 stroke oil, considering how far a 1 ltr of oil will go its worth getting the top of the line oil...

CB

It's air/fuel in jetting, not fuel/oil. Leave the ratio as it is, it's not the problem

[quickbuck]

Also, nowhere has the OP said the actual heat range of the plug he is using... Could well be an NGK 10 (Or Champion 1 ie COLD!), that will do it every time if you even get out of the power...
Heat range would be the first thing to check.

[Paulus]

Yea, got that out of a motorcycle mag about turning the fuel off and running the carb empty works a treat!

Actually this works well on my Husky too. If I don't run it out of gas before I transport it on the trailer then it will be flooded for sure when I get to the riding area and a bitch to start. Run it out of gas beforehand and it starts second kick every time.

A friend has/had (its being replaced) an old KDX250 and it is always fouling plugs. He went back to stock jetting and checked (and double checked) everything. Decoked pipe, repacked silencer, rebuilt engine, hotter plugs, new plug lead, etc, etc. In the end a mechanic said that the carb was too worn and that was causing it. Maybe that was true? Its been to hell and back a couple of times.

[Danger]

Have you checked or adjusted your float level? Checked your overflow hoses are not kinked or blocked? I don't think your bike was designed to flood but does the Husky owners manual say to run it out of fuel before stopping everytime? Who knows, I never owned a Huskie other than my chainsaw and my chainsaw manual does not offer this advice so I kind of doubt it.

And going back to stock jetting at this time of year means that you will still be running far to rich on most bikes. Most bikes come from the factorys rich to protect the consumer and the shop owner from the consequences of running too lean. And thats in winter time. Once you get into the heat and humidity of summer things only get worse.

Running the bike out of fuel, reving the shit out of it, running hotter plugs, they are not the answer for overcoming a poor running bike. No wonder there has been this mass exodus of riders to four strokes with people running their two strokes with bad jetting and having to resort to some of the procedures listed here. But with a little effort a well jetted two stroke will put a smile on your face wider than the lines the four strokes have to take around the track.

For a 250 I would run a good oil like Motul 800 at 50:1 (we are talking a trailbike here not an MX bike) and be aware that this will make the bike run richer with the same jetting (cause the fuel will flow faster through the jets with less oil in it). But the jetting obviously needs looking at anyway. Main jet, jet needle position, pilot, and airscrew at least will all need to be looked at and adjusted at the very least. In some cases a leaner needle or slide could be needed or the existing cutaway filed leaner. Not sure on the specifics of the KDX250 but some further research should prove fruitful in these days of the internet. Don't put up with a poor running bike, its no fun.