Gx 340 surging

Hey guys, new to the site but not the garage. I have a generac generator powered by an 11 hp Honda gx340 engine. I was running it last week and it would surge, stumble and literally shut off for a micro second and then catch and run normal for 2 mins., 5 mins. or however long and then do the same thing. We have winter around the corner and I wanted to get this thing running right for when I need it. Here is what I have done so far, installed new carb, new ignition coil and spark plug and I cleaned the gas tank, shut off valve and small fuel filter screen in the tank. When I start it now, it will only run with the choke closed and yes it still surges???? When I open the choke she immediately stumbles and dies. I did find that I was able to stop the engine from surging by manually adjusting the auto throttle solenoid assembly arm which works in conjunction with the governor arm. I am trying to find a testing procedure for this solenoid before I throw out $65 for it. Has anyone had any experience with these solenoids? Any and all help is greatly appreciated.

axcessadam said:

When I open the choke she immediately stumbles and dies.

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That's a classic symptom of a clogged or blocked main jet inside the carburetor; with reduced fuel flow, the engine won't run at all unless you also reduce the air flow (choke). When you open the choke, that's allows too much air, and the engine dies.

How old is the fuel? If you allow fuel to remain in the tank for more than 45 days, it has likely decayed and formed gunk inside the carburetor.

Need to pull the carb and have it totally cleaned, with particular attention to the main jet and nozzle (yellow highlight below). With the engine serial number (stamped on the side of the block (GXXX-1234567) you can shop for a whole carb (list price: $73) , and much easier/faster to swap out than to clean an old one.



FYI, the auto-throttle device is made by Generac, not Honda, and I'll boldly predict it is working okay. Somewhere in a Generac shop manual is a procedure for testing it, I would guess.