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Hey guys, any ideas would be greatly appreciated on this.*

So it started a few months ago, riding with some buddies and my 400ex all of a sudden lost power. Wouldn't fire, wouldn't sputter. Towed it home, and then it fired right up. It continued this pattern for a week or two, ran perfectly for varying amounts of time, suddenly died, and would start right back up if I waited 20 mins or so.

Now we get to the next phase... I was dinking with it one day, I think I pulled the carb off and cleaned it out, (not really dirty but just to be sure) and I was trying different fuel screw adjustments. At any rate, I didn't notice much change, except obviously running a little poorer when I had the fuel screw in the wrong place. I took it on a quick ride around the block, and it was just fine. Ran awesome, had lots of power, etc. Then went around the block again and it died on me this time right as I revved it. Ever since then I haven't been able to get it to start.*

Now when I turn it over, it sputters, fires a touch, but won't start. Ever. I replaced the plug, CDI, and coil, with no change. I do know that it has spark, but I don't know for certain that its big enough. After replacing these with no change I popped the carb off and tried firing it up spraying some either right into the intake. Upon doing so, it revved right up, but obviously there was no carb so it didn't stay running for long.*While spraying the ether it seemed to run just like other engines I've tried spraying ether into no popping or backfiring etc. When it fired right up on the ether, I figured I must have a carb issue, so I just bought a whole new carb instead of taking the old one apart for the 800th time. When I put it in, there was no change whatsoever. Still turns over and sputters, but won't fire up.

I am completely befused, and any input would be graciously accepted. If you read through all that your a trooper, so thanks very much :)*
 

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Welcome to the forum. I would think it could be the stator but have you checked things like valve lash and timing chain slack. Do you think the cams could have got out of time. You might want to check the compression. Could be time for a top end rebuild.
 
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