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Discussion Starter · #1 ·
It's a 12.5 hp Briggs (219807-0389-E1). The carb is brand new (593432), and I cleaned it anyway just in case. There is no air filter yet, so it's got plenty of air flow. I adjusted the valves today because it was spitting and popping, so those are good.

The engine will idle fine. If I increase the throttle very slowly it will stay running all the way to full throttle. If I increase throttle any any speed above glacial, the throttle plate flips to wide open and the engine dies. It's very touchy. The throttle searches and races a little when the engine is cold, then stops after a minute or so. Once it's warm, the throttle stays closed even at full throttle and only opens if I increase throttle too fast, then it flips wide open and the engine dies.

The breather tube is tore off and has been ordered, so it doesn't have one right now. The spark plug is old, and I'll replace it tomorrow.

So my future attempts for solutions are new sparkplug, new breather tube, and new air filter. Just in case it's not any of those, any ideas? This throttle plate/governor arm acting strange has my curiosity.
 

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Discussion Starter · #3 ·
This was a basket case when I got it. Didn't have the air cleaner. Should be here in a few days.

It did get a little better with a new sparkplug today, but still easy to kill the engine by pushing the throttle up too fast. It's hard to see with the valve springs in the way, but the exhaust valve guide might be working it's way out. I'll check that when I replace the head gasket. Compression test this morning showed 100 lbs, so I think the valves are seating fine.

Holding the choke manually fixes the problem. Not that that is a solution, but it tells me something. Don't know what, but something.
 

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If holding the choke helps…presumably closed some. That means it is running lean(ie not enough fuel). Air filter will probably help, but either adjust the main jet open a little bit. Also you said the carb is new. Is it a Briggs carb or a chinesium carb? One last question, when opening up the throttle, are you sliding it up, or cracking it wide open?
 
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Discussion Starter · #5 ·
If holding the choke helps…presumably closed some. That means it is running lean(ie not enough fuel). Air filter will probably help, but either adjust the main jet open a little bit. Also you said the carb is new. Is it a Briggs carb or a chinesium carb? One last question, when opening up the throttle, are you sliding it up, or cracking it wide open?
Yes, holding the choke closed fixes it so I can flip the throttle back and forth between full and idle as fast as I want and it won't die. The new carb is a generic Nikki clone. It has one adjustment knob that I used to get it idling smooth and slow. The issue I'm tackling is that the engine will die if I increase the throttle. The new sparkplug made it so it's not as touchy. It went from ridiculously touchy to just very touchy.

If the air cleaner and the breather tube each make it just a little bit better, then it will probably be good enough for use. As it is, it would be constantly dying every time I increase throttle without remembering to move it extra slow.
 

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My guess is that that carb doesn’t have a main adjustment, just the idle. Most new carbs are set lean to begin with. Can you post some pictures of the carb?
 

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Discussion Starter · #7 ·
I stuffed the air cleaner full of toilet paper. Problem solved. Unbelievable. I can flip the throttle from idle to full as fast as I want and it stays running with just a little hesitation. Take the toilet paper out and it goes back to dying. Should be fixed when the proper air filter arrives.

Carb doesn't have a main adjustment, just the idle.
 

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Discussion Starter · #11 ·
It wouldn't turn over this morning. Cylinder full of gas. Suspect needle and seat, but the carburetor is brand new. Replaced the new needle with another new needle from surplus rebuild kits. Fuel shutoff solenoid was disabled when I got it. Could try to find the wire to get it working again and see if that helps keep gas from getting through when it's not running.

Took the flywheel off to get to the breather. Replaced the torn breather tube. Put it all back together. Removed tissue from air cleaner. Ran the engine and it throttles up and down just fine.

Will have to check the oil for gas, but it wasn't smoking at all, suggesting the oil level was not increased by gas getting past the rings. Currently dry, so it won't leak back in.

Solid morning. Thanks to all.
 

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Discussion Starter · #13 ·
I have one, but I'm not in the habit of shutting it off that way. I could definitely do it that way if I was keeping it, but this one's getting sold in a couple of weeks when it warms up.

"Before you buy this, let me explain what doesn't work right." I'd prefer to avoid that. I'm testing the float right now to see if it's still leaking.
 
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