i keep fouling spark plugs???

[tom-s]

2 weeks ago i bought a 250 supermotard sm 2002 and ever since i got it home it has been fouling spark plugs.
i got it from a friend who has said he never had a problem with it but i have only been able to get a few miles out of it before it fouls the plug.
i have had a look through some other threads but still would like any advice that people can give me.
so far i have gone through a few different plugs but the same thing happens every time.
plugs tried - BR8EG, BR8EVX, BR9IEX, BR8ES AND B8EG
tonight i have taken the carb off to check the jets and have a 185 and 40 in there with a #7 slide, the needle was on the 3rd position out of 5.
i have read that it should be on the 2nd but dont know if that means from the top or bottom out of the 5 that are on it.
i also read that a ltr jet kit would help or it could even be the cdi unit but dont know where to start
so all in all im a bit stump and any suggestions would be great

[wence]

Originally Posted by tom-s

2 weeks ago i bought a 250 supermotard sm 2002 and ever since i got it home it has been fouling spark plugs.
i got it from a friend who has said he never had a problem with it but i have only been able to get a few miles out of it before it fouls the plug.
i have had a look through some other threads but still would like any advice that people can give me.
so far i have gone through a few different plugs but the same thing happens every time.
plugs tried - BR8EG, BR8EVX, BR9IEX, BR8ES AND B8EG
tonight i have taken the carb off to check the jets and have a 185 and 40 in there with a #7 slide, the needle was on the 3rd position out of 5.
i have read that it should be on the 2nd but dont know if that means from the top or bottom out of the 5 that are on it.
i also read that a ltr jet kit would help or it could even be the cdi unit but dont know where to start
so all in all im a bit stump and any suggestions would be great

I run my 300 on 180 main, 42 pilot.
Main in middle clip.
Motul 800 at 45-50:1.
Powercore2 muffler.
All cool.
Mark

[gasgasandrew]

I,d say look at crank seal on gearbox side maybe sucking oil in has this bike been stored before you got it doe's it smoke a lot????

[tom-s]

it wasn't stored but only used as a bit of fun at weekends, only smokes a bit till warmed up then looks fine. If the seal has gone how would the plug look because it doesnt seem to be oiled up at all

[iancp5]

I would think for an SM you need slightly different jetting to dirt. Very likely slightly larger main but the rest could be a tad leaner with a larger main. I don't know that for a fact though. Just thinking you'll be spending more time on the main than dirt bikes and you don't want to run too lean / hot.

[slocalspode]

I think the OP said he was running a 185 main. That is pretty large.
I have a 1998 EC250SM conversion.

I am running the LTR supplied needle in the third clip down from the
top. With a 178 main and a 45 pilot. Using a #7 slide.
I have VERY little spooge out the pipe and I have never fouled a
plug. It idles smooth and seems to me. To pull well in a linear drive.
The only time it sees any real throttle is on acceleration from a
stop light or up a hill. I use mine as a street putting fun machine.
In a steady 50mph cruise. I'd guess the throttle is not open
more that 1/8-1/4 of the way. I think my gearing is a 14/47.
I do re-pack the silencer fairly often though. Maybe every 300-400
miles, or less.
BTW, I am @ sea level most of the time. With canyon rides up to
3,500-4,000ft.
YMMV, Jeff, So. Cal. USA

[jostby]

My '00 XC250 would foul the plug almost every time I rode slow like a long downhill or following my son (when he was young!) or maybe like riding in traffic? (plus excessive spooge) The LTR kit needle change made a huge difference but the weird part was the idle jet went from a 42 to a 48 (??) Don't ask why but with the needle it works real well. He had supplied a 175 main jet but the original 185 worked best for me. I know that is against what most folks here run but I wonder if the earlier "XC" bikes had some type differant ignition curve?
I get almost no "spooge" when I ride it like it is intended to be rode. I also use the B8EG (?) non-resistor plug and have never fouled a plug since and that has been about 7yrs. And I used to use 2 or 3 per day. ($$!)
edit.. I do have a #7 slide too.

[stay_upright]

What do the fouled plugs look like? I would be tempted to move the needle clip position one higher (drops the needle more, is leaner at 1/4-3/4 throttle position) to see if that improves things.

What's the mileage on the bike - it could well be the emulsion tube in the carb is worn (wears from the needle rubbing on it) which would make it run rich I guess a 2002 SM may of had a lot of use. I don't think it's possible to replace the emulsion tube however it woudl be possible to re-jet around it.

Also what needle have you got - remove it completely the numbers on the side and check for any signs of wear scuffing scratches etc.

Incidentally iriduim plugs have the best resistance to fouling though cost a bit more but it sounds more like you ned to sort out whatever is causing the problem in the first place...