Help me diagnose sputtering in 20hp V twin Intek please.

Elkins45

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  • / Help me diagnose sputtering in 20hp V twin Intek please.
I’ve asked about this engine before but the suggested fixes didn’t work. I bought a used mower primarily for the deck and transmission but it did come with an engine that started and ran, but it has a random intermittent deep sputter. People suggested it was a fuel supply issue because it seemed to happen more under load, but I’ve replaced the fuel line and swapped in a good carb I scavenged from a running engine that grenaded and replaced the fuel pump and vacuum line and it still does it. It will even do it occasionally when just sitting still not under load, but just for a couple of seconds.

One thing I did notice today was a bunch of exhaust coming out of the area around the exhaust manifold gasket (or maybe the head) on the same cylinder as the fuel pump vacuum tube. Could a blown head gasket cause an intermittent loss of power?
 

Rivets

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  • / Help me diagnose sputtering in 20hp V twin Intek please.
Definitely! Pull the plug on that cylinder and notice how it starts and runs. Put the plug wire on and repeat on the other side. If it runs the same with the bad cylinder unplugged and runs worse with the good cylinder unplugged, I’d put money on a blown head gasket.
 

Elkins45

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  • / Help me diagnose sputtering in 20hp V twin Intek please.
Definitely! Pull the plug on that cylinder and notice how it starts and runs. Put the plug wire on and repeat on the other side. If it runs the same with the bad cylinder unplugged and runs worse with the good cylinder unplugged, I’d put money on a blown head gasket.
The leaking side actually ran better LOL.

I went ahead and mowed a small section of the yard with it after replacing the plugs. It sputtered and even died a couple of times but I kept going until I finished. After I parked it I lifted the hood and heard a sound I’ve never heard from a mower before. There was a sound that was remarkably like water boiling. I thought at first it was coming from the float bowl but after moving around a bit I’m not positive it wasn’t from the valve cover. This thing is odd to say the least.

I did notice that it seemed to sputter more frequently when I was making a hard left turn. That makes me want to think it’s fuel supply related again.
 
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