Spark Plugs

[Dave400ex]

I went out last Wednesday and the 400ex started right up. Then on Friday I went out to go Riding. It might have been 10-15 degrees cooler. The 400 would not stay running with the Full Choke on. I tried Half, and none and it wouldn`t stay Running. So finally the Plug fouled out. So I took it out and it was Black. I got a New One and got it ready to put in. Everything should be fine on the New Plug. Well I have everything back together, go out and try Full Choke, nothing, Half Choke, nothing. It sounded a little different too. I have no idea what is going on. We are going to check out the Plug some more tomorrow. Any Ideas?

[JustRace]

Best of luck! The problem you had with idling was the exact same problem with my ex. I just pulled the plug and cleaned it and leaned out the mixture before I started it and now it runs fine.

But its odd that you fouled the plug. Usually when it gets colder the air is denser, so it should have actually leaned out the mixture.

[Dave400ex]

Mine does kind of Idle weird. When it starts it will Rev really High and then if you don`t give it Gas for a while it almost sounds like it is going to Die. Should I turn the Idle Screw some? I really don`t know what to do. I will change the Plug today and when it`s Warm again I will try to start it. If it doesn`t Start then I`ll take it out to my Buddy Jason and let him Work on it. Anymore Ideas?

[trx400ex]

mine used to do that everynow and then...but it only would do it once then it would start up after a new plug and dry cylinder

[Dave400ex]

Yeah if I put a New Plug in it should Start right up. If not I have more then a Jetting Problem.