2 stroke question

[trx450jason]

Didn't really know where to ask this. Im pretty mechanically inclined and work on all of my own stuff but know nothing about 2 strokes. Anyway, my friend has a CR125 that fouls spark plugs like crazy. Almost every other time he rides. What could cause this? Maybe the fuel/oil mixture?

[wilkin250r]

I doubt it would be the fuel/oil mix. You've got to add a LOT of oil for that to be the cause. I doubt he is mixing 16:1 premix.

Most likely it's his JETTING that is causing his fouled plugs, he's probably running a bit rich.

[GPracer2500]

Probably jetted wrong. Could be a clutch-side crank seal that's leaking but definitely look into the jetting first. It's doubtful that it's the fuel/oil mixture. Even down to probably 20:1, if you're jetted correctly you should not foul plugs all that frequently. Also make sure the correct heat range spark plug is being used. Running too cold of a plug can promote fouling.

Does he put-put or ride aggressively? Chugging around off the pipe will exacerbate plug fouling.

[GPracer2500]

You're fast wilkin! :p

[trx450jason]

Most just puts around on it. Doesn't ride it as hard as it should be rode. Sounds too me like a combination of this and running rich.

[wilkin250r]

Originally posted by GPracer2500
Chugging around off the pipe will exacerbate plug fouling.

I have heard this from several sources, but I've never SEEN it. I've run off the pipe many times (sometimes as long as a half-hour straight), yet I've never fouled a plug because of it. I still think it comes down to a jetting issue, even on the idle circuits.

[RiderTRX400ex]

i know when i had my old KX, after a top end rebuild i started to run the spark plugs that the service manual recommends and the bike no matter what would foul them out all the time.. i ended up switching back to a BR9ES and never had the problem again...

[GPracer2500]

Originally posted by wilkin250r
I have heard this from several sources, but I've never SEEN it. I've run off the pipe many times (sometimes as long as a half-hour straight), yet I've never fouled a plug because of it. I still think it comes down to a jetting issue, even on the idle circuits.


Exacerbate, as in make a pre-existing condition more pronounced. I was trying to say that a condition that is allowing a plug to foul will be more evident if the engine isn't run hard. If he puts around most of the time then his jetting may not be way off--just not quite right. If he's fouling a lot of plugs AND he's always running 90%+ then his jetting could be pretty far off.

That's what I was trying to get at with that comment.

[250r4life]

Originally posted by wilkin250r
I have heard this from several sources, but I've never SEEN it. I've run off the pipe many times (sometimes as long as a half-hour straight), yet I've never fouled a plug because of it. I still think it comes down to a jetting issue, even on the idle circuits.

my old atc 250r was like this... if you didnt ride that sucker hard it would foul plugs... my buddies old LT 250r was the same way... both had had some extensive porting, and i know at least the LT was on the rich side trying to keep it from burning up (good ol Suzukis...)...

but yah, my 89R never fouls plugs... i can put and do whatever i want, and that thing still runs...

[250r4life]

my advice would be to tell him to ride it a little harder... if anything just done be so ancy to shift gears, wind it out a little more....

be carefull about trying to lean it out and end up burning up a piston... plugs are a lot cheaper than top ends...

[250r4life]

one last thing... you may want to try one of the iridium plugs... like a B8EIX...

i've heard that those suckers are super hard to foul, but maybe wilkin or GP can confirm that...

[Toadz400]

Originally posted by 250r4life
one last thing... you may want to try one of the iridium plugs... like a B8EIX...

i've heard that those suckers are super hard to foul, but maybe wilkin or GP can confirm that...

I can confirm that the Iridium plugs are indeed harder to foul. I switched from normal NGK's to the Iridiums on my Banshee and I didn't replace the plugs for close to a year running slightly rich jetting.

[86 Quad R]

i agree with what was said about puitting around and the "pilot jetting" being off a bit.

i occassionally trail ride with the family (usually about 8-10 quads) and we average about 16 miles at slow paces. infact, the last time we rode i think i got into the pipe 3 times and have yet to foul a plug.

[speedfreek]

If nothing was changed lately and it is getting worse it would be his STATOR.