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250sx plugs fouling

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Ive got an 05 250sx. I had a cracked ring and did a top end, no cylinder damage luckily. Now im fouling plugs after one day riding like clockwork. it will run fine all day. When you go to cold start the next it fouls. The jetting has always been on, and i have tried leaning it a bit with no reponse. Aynone think it could be a faulty CDI that is burning up the plug? At least there only 12 buck a pop! Kost Too Much thanks Gary::)

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Well when you had a cracked ring...and even far before it cracked it was probably running leaner. If you touched the jetting then or if it was running perfectly at that time then you are probably running it richer now with the top end. Go through all of the jets and make sure they're spot on. Since you did the top end/since you have been fouling plugs has anything else changed? Is the power the same? Is it smoking? Are you running the same type of plugs? Are you doing the same kind of riding? Running the same gas/oil/mix ratio? Did you clean the powervalve and reinstall it correctly? What does the plug look like when you remove it after fouling? Make sure your reeds are perfect and tight. If the reeds are tight then hold them up to light and see if the tips are more transparent then the lower area. This can mimic rich jetting and make you think that the jetting is rich.

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Also, I'm sure there is a cheaper plug that you can be running until you get it fixed. What plug are you using?

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The only other thing i can think of is i took a pretty good crash on the front bent the handle bar perch and jolted the bar stop real good. Don't know if that would do it. Ive been over almost everything i can think of I set the jetting to stock 168 main and the needle positon at the second notch thats 2 steps leaner than stock. Im running 45:1 mix if im in wide open riding it might get two days riding out of it.. as soon as i hit trails or techincal stuff its done for. maybe a 165 main would help. I thought i read somewhere about a CDI problem that caused this same thing but i hate to spen $300 just to find out. maybe it was damaged when i crashed?????? Gary

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They call for the BR8ECM for some reason I dont know if i could use a cheaper BR8 or not

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You can use a br8es for now, they are cheaper. When its good to go then go back to the expensive plug. If the plug lasts a while under wide open riding then Its probably not the main jet. When you are in slower technical spots you are using the pilot and needle jet more. Does it smoke or bog? Look at the ignition box on the headset of the frame holding your bars. If the black box is damaged then its the CDI unit. Check the reeds am make sure they're flat against the cage with no space .

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Theres no apparent damage to the CDI But i cant say enterally. It will start to bog out after extended techincal sutff usually i can clear it out if it's hot and can open her up. IN that case it will definatly foul on the next cold start. maybe lower the pilot jet a size or ive heard about using a yamaha needle i don't know the number though... maybe just get rid of the austrian pig.

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You definitely dont want to get rid of the bike, they are the best of the best. You just have a probem somwhere. I'd say you need to warm the biek up completely and then shut it off. Turn the pilot air screw all the way in intil it stops turning easily. Then turnit out 1 and 1/2 turns. Start the bike up and make sure it warm. Adjust the idle speed screw(usually black plastic with a spring wrapped around it) until it has a very slightly high idle. Then turn the pilot air screw slowly in each direction. When it brings the idle speed up as high as it can(it wont be too much) then you need to see where the pilot air screw is. If its more than 2.5 turns out, its too rich, if its less than 1 turn then you need a bigger pilot jet. Its sounds like you need a larger one though. If you are needing to clear it out by revving it up then you're probably getting too much gas and you just need a smaller pilot jet and to adjust you pilot air screw after. If you adjust the pilot air screw in and out and the idle speed doesnt increase then you either have a pilot air screw that is WAY too rich or you have a dirty carb.

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Ill give it annother try this evening and see what happens thanks for all the good info

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are you turning your gas petcock off at the end of each day of riding? Does it foul the plug when the choke is on at first start up or after a few minutes? To lean wont foul a plug unles it is so lean that you are melting the piston and the little melted balls of alum are sticking to the plug electrode.

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The #1 cause of plug fouling is having too fat of a pilot jet!

There is no one jetting spec. that will work year around in all temperature and elevations. You have to change your jetting when it gets warm in the summer or cold in the winter. If you are jetted for winter and you are riding in the summer your bike will run to fat. If you are jetted for summer and you are riding in winter your bike will run to lean.

I get over two years out of my plugs. I am on my second plug on my '06' 250sx.

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though I agree with Larry, there is proof of faulty ignition systems causing the cold start fouling. I know of 2 people locally, that have had this issue. It got to a point where they would just install a new plug before each ride. Theirs would foul the plug upon restart also, after sitting for a little. Electrical issues can be a :) , so as suggested, I would start with the simplest fix first, the pilot circuit.

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Well i ran the bike yesterday with a BR8ES plug and it ran great. i only was on open trail and some hill climbs. Its an amazing bike when it's on. I think that it just want's to be run hard or not at all. Im gonig to see if she will start again today. Probably drop the pilot jet to a .40 from the .42 see what happens.

On annother note any opnions about a 625 sxc? Potential Trade. Too Heavy?

Never been on one Thanks too all

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I had an 01 250sx that I rode in the woods. Since new, it would burn 3 plugs every ride. I tried to jet the problem by leaning it out to the point where throttle response was an issue, but the plugs would still foul. I then tried a BR7ES plug and had no problems after that. I even returned to the stock jetting.

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The BR8es plug and leaner pilot jet seem to have done the trick. I think the plug was the key. I lugged the bike up some nasty horse trails and no fouling or even loading up. Also im not boiling over anymore. I had almost forgot how bad ass this bike really is. cheers

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Same problem: http://www.thumpertalk.com/forum/showthread.php?t=663926

Once I got her going, it would start warm on the first kick every time all day. Let it sit overnight or more and it was trouble. On the very first kick, it would start to go then die. Then it was fouled.

I started shutting off my petcock before I shut the bike off. I shut off the petcock and let it run about 30 seconds but not until it sputters out. It has worked well so far.

Make sure your air filter is not over-oiled and not allowing air to flow through.

I have always used BR8ES without problems.

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