Plug fouling 250XC. Help!

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SteveOg
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Plug fouling 250XC. Help!

Post by SteveOg »

I'm down in Idaho and have had an issue come up with my bike. It's a 2012 250XC with about 53 hours on it. Last ride I did was about 40km and the last 10 or so was a fairly ugly downhill where I was in first gear letting the engine slow me down. Bike ran great the whole ride so I loaded it up and brought it to the house. Today I went to ride again and put in a new air filter, topped up the fuel and drove to the staging area but couldn't get the bike to start. After kicking until I had nothing left, I pulled the plug and it was soaked with oil. I didn't notice a smell, but it was definitely black and oily. I put in a new plug and the bike started first kick and off we went. Rode about 23km, on and off the pipe, and then on a long downhill the bike died. Coasted to the bottom and it wouldn't start, so I pulled the plug again to find it was soaked. Wiped it off, put it back in and it started but only ran for about 20 seconds before dying again. Again I pulled the plug and it was oily, so I started pushing for 3 miles while my buddy went to get my truck.

I've never fouled a plug in this bike and I believe it's jetted well for here and has performed great the last few rides. I did notice I had no spooge from the pipe last ride or today, which is unusual because I normally wipe it off after the ride. I'd like to be riding again on Saturday and have a few weeks left here and want the bike up and running. Any suggestions? I don't know where to start. It's crazy dusty so I'll change the air filter again in the morning and change the oil to see how much comes out to hopefully eliminate a blown seal, but would love your guidance on what else to try. Thanks!

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cedric
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Re: Plug fouling 250XC. Help!

Post by cedric »

Sounds rich, drop your needle a clip and see if that helps.

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Re: Plug fouling 250XC. Help!

Post by SteveOg »

I've done 6 or so rides with this jetting with no issues but all of a sudden it fouls a plug in 20km. I don't know a ton but it seems weird to me that the jetting is suddenly off enough to cause that much oil on the plug. This is a ride I've done twice before, and as part of an 84km loop with no issues.

I'll try the clip but if it's rich, wouldn't I see more spooge instead of less?

Thanks for the advice. I'm really at a loss and appreciate any and all suggestions. It's killing me not being able to ride while I'm here and have a buddy bringing his bike down soon to join me, so I'd really like to resolve this.

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Re: Plug fouling 250XC. Help!

Post by Shibby! »

Few things.

1) What's your elevation? Idaho varies wildly.
2) You mentioned it's extremely dusty. Keep the air filter clean. A dirty air filter can cause it to run rich. Filter skins help A LOT. Simply pull off and ride another day with the same filter. They can clog up quick though (which is what they are designed to do)


Hopefully the fouling plugs isn't due to the stator/coil, etc. Doubtful on a bike this new. The wet plug was likely because you were coasting down a hill with the engine off. Just because it dies doesn't mean it's not sucking fuel in under vacuum. Even pulling the clutch in has enough drag on most bikes to keep the motor turning over.

When you coast down a hill or under engine braking and get back on the gas does it bog or seem sluggish for a split second? It should feel crisp and quick. If not, likely rich jetting.

Where are you? You'll need to do a report on which areas you rode. We had some great riding down there this spring.

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Re: Plug fouling 250XC. Help!

Post by Jonny5 »

Maybe some dust got in the carb? It could be affecting the float needle? I would pull it and give it a cleaning.

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SteveOg
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Re: Plug fouling 250XC. Help!

Post by SteveOg »

Shibby! wrote:Few things.

1) What's your elevation? Idaho varies wildly.
2) You mentioned it's extremely dusty. Keep the air filter clean. A dirty air filter can cause it to run rich. Filter skins help A LOT. Simply pull off and ride another day with the same filter. They can clog up quick though (which is what they are designed to do)


Hopefully the fouling plugs isn't due to the stator/coil, etc. Doubtful on a bike this new. The wet plug was likely because you were coasting down a hill with the engine off. Just because it dies doesn't mean it's not sucking fuel in under vacuum. Even pulling the clutch in has enough drag on most bikes to keep the motor turning over.

When you coast down a hill or under engine braking and get back on the gas does it bog or seem sluggish for a split second? It should feel crisp and quick. If not, likely rich jetting.

Where are you? You'll need to do a report on which areas you rode. We had some great riding down there this spring.
I'm in Coeur d'Alene (I've got a place here and spend the summers here) but you're right that the altitude changes a lot. We've been riding between 3-5000 feet the last couple of rides.

I'm pretty good with air filters and have 8 of them with me. I change it every ride and then clean and oil them all at once.

I wasn't coasting down the hill with the bike off until after it stalled out, so I'm assuming the plug had fouled at the top of the descent, but I kept rolling to get out of the trees and catch the guys I was riding with. It may have a very slight bog after a long downhill but not much. I can try and lean it out a bit and see what happens. What surprises me is that it has been running great until it fouled back to back plugs. This is the first time I've fouled a plug on this bike, ever. I don't ride the bike hard, typically because the trails are tight and I'm still a little nervous recovering from an injury but yesterday we did a lot of long climbs and I was on the pipe a lot more than normal. I can move the clip and lean it out a bit to see if that helps.

Jonny5, with how dry it is, dust could be anywhere so I can check the float. Im going to wash the bike really well this morning before I start taking stuff apart and see what happens.

Thanks again guys for the advice. I'd like to get this solved ASAP so I can get out riding after the rain early next week. It's been a long time since the trails have seen some moisture and the powdered sugar I'm riding in now is losing its appeal.

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Re: Plug fouling 250XC. Help!

Post by trailguy »

I would try the leaner clip position and clean the carb as mentioned. When your into the carb you may want to check the Reeds for a chip or crack.
Check that the Stator bolts are tight. Its possible the crank seal is going on the clutch side, but unlikely given the low hours.
My guess is because you were using 1st gear to slow you down on a steep hill for 10K it may have created an obnormal amout of suction in the crankcase and sucked in a small piece of the center case gasket, resulting in tranny oil entering the crankcase.

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Re: Plug fouling 250XC. Help!

Post by SteveOg »

I moved the clip up one notch and the carb looks clean and reeds are good. I checked the oil level to see if I had been pulling oil from the tranny and it's still full, sitting at the top of the level hole. I know that isn't a perfect tell, but I haven't lost much. I put in a new plug so I guess I'll change the air filter and put the tank back on and see what happens. Hopefully it'll run ok.

If you think of anything else to check, let me know. Thanks!

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Re: Plug fouling 250XC. Help!

Post by Dobi »

I would check the pilot jet. it seems weird, but a plugged pilot can cause a bike to run rich and boggy and will foul plugs. I have used a bristle from a bbq brush to slide into the small hole inside.

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Re: Plug fouling 250XC. Help!

Post by SteveOg »

Dobi wrote:I would check the pilot jet. it seems weird, but a plugged pilot can cause a bike to run rich and boggy and will foul plugs. I have used a bristle from a bbq brush to slide into the small hole inside.
Sounds good. I think I'll go for a short ride and see what happens after what I've done and if it does, pull the carb completely and go through it all.

Thanks fellas!

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