Hello

I have a Duromax XP10000e generator powered by a 439cc engine.

This generator has about 5-10 hours of use on it. Not too long ago when starting, it started surging and after a few minutes it would die. It was a an absolute pain to restart only for it to die.

I tore down and cleaned the carb. No difference. I've since replaced it with two more brand new carbs and gaskets... no change. I replaced the gas. Nothing. I even replaced the fuel line, no change. I've checked valve lash clearances to make sure they're in spec. I've inspected and checked the gap for the spark plug. No change. A compression test showed 90psi. I confirmed thatbthe governor isn't responsible by disconnecting it from the carb.

I can start the engine cold realatively easily with the choke and throttle fully closed. It will only run after that with the choke fully off and keeping the throttle closed. Opening the throttle causes the engine to stumble and die with a second or two. I've noticed that with the throttle open, fuel spits out. I can keep the throttle open and the engine running with staring fluid, though it backfires thru the carb frequently. Finally, with the engine off I can feel air pushing out thru the carb when pulling the starting cord. That last detail seems to be the culprit, but what would cause that because I confirmed valve clearances and compression?

Much thanks

Did you clean/ at least check the fuel filter in the fuel on/off valve?
 
While there, disconnect the fuel line from the carb, turn on the fuel (catching it in another container), and see if you get adequate flow from the line.  
 
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Thanks for the response. I neglected to mention that I did confirm unrestricted fuel flow and the condition of the shutoff filter.

Does the engine run to full RPMs (normal temp) with the choke butterfly mostly closed?
 
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Once started, it will only idle, choke off, throttle closed. Idle speed is way below 3600rpm.

On your carb, is there a black, plastic idle "stop screw" (combo Philips / straight head).?
 
If so, did you remove that and get to the idle circuit jet underneath it? That jet is extremely small
and does clog often.
 
A piece of wire, from a wire brush, clamped in a vise grip is about the only thing that'll clean it..
 
.

Completely tore down the original and then the second carb. Soaked the units in carb cleaner for 24hrs each, then cleaned with carb spray everything including the idle jets. Didn't bother with the third, brand new carb since the engine behaved identical to the first two carbs.

I am convinced the problem lies beyond the carb. Its blowing air out the intake and carb.

Beginning to wonder if it has a worn exhaust cam lobe, which would limit the amount of time the exhaust could escape causing it to push exhaust out the carb.

You could see how much each valve travels simply by pulling the valve cover and slowly cranking over. 
 
Might want to check the flywheel keyway..
 
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