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400EX Won't Stay Running

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Old Jan 18, 2009 | 02:59 PM
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Default 400EX Won't Stay Running

I just recently rebuilt the engine top end. And I'm having trouble keeping it running. I tore down the carb and cleaned it yesterday and reinstalled it today. Fired it up and it ran for maybe a minute and half then died.

Could the plug not be hot enough?

Could the timing be off a little bit?

Any suggestions would be great.

Thanks,

Brian
 
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Old Jan 18, 2009 | 03:41 PM
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Default 400EX Won't Stay Running

Timing, valve adjustment, cam, rings, piston,,,,, could be any number of things.
I'd say it's time to take the top end off again and have a look.
I dought it's the spark plug.
 
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Old Jan 18, 2009 | 04:57 PM
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Default 400EX Won't Stay Running

how is it dieing? runnig out of gas...just cuts out..or something els? are you using any choke?
 
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Old Jan 19, 2009 | 12:40 PM
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Default 400EX Won't Stay Running

<div class="FTQUOTE"><begin quote>Originally posted by: Red400EXRod

Timing, valve adjustment, cam, rings, piston,,,,, could be any number of things.

I'd say it's time to take the top end off again and have a look.

I dought it's the spark plug.</end quote></div>

I re-adjusted the valves yesterday and had it running for a good 3-4 minutes at idle and high RPM. Then it died out again. May need to make some more adjustments to the vlaves and possibly the pilot valve.
 
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Old Jan 19, 2009 | 02:22 PM
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Default 400EX Won't Stay Running

Runs and then dies,,,, sounds like a fuel starvation problem.
How long do you have to wait until it will start again?
 
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Old Jan 19, 2009 | 02:44 PM
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Default 400EX Won't Stay Running

<div class="FTQUOTE"><begin quote>Originally posted by: Red400EXRod

How long do you have to wait until it will start again?</end quote></div>


Several minutes and then it will start up.
 
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Old Jan 19, 2009 | 04:01 PM
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Default 400EX Won't Stay Running

Definately sounds like fuel starvation.
 
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Old Jan 19, 2009 | 04:22 PM
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Default 400EX Won't Stay Running

Sounds like the bowl is not filling up since it runs for a few minutes then when it dies takes a while before it'll start back up. Make sure your float is working properly.
 
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Old Jan 20, 2009 | 02:21 AM
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Default 400EX Won't Stay Running

agreeded, float problem. pull it apart and clean. also the fuel line from the tank and make sure there is no trash in it
 
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