Gx390 issue

Having some Equipment issues, Honda Gx390 wanting to stall once you let off the trigger. Black exhaust, PAI to start and a flame every now and then will join the party once I shut the machine off. From what I’ve read it could be the ignition coil or may need a carb cleaning ? Any suggestions which route to go down first ? Machine is one year old, new oil , spark plug, filter and pull cable. Was not stored the absolute best during winter… any help I’d appreciate it.

Have heard if they are hard starting valves could be out if adjustment


Interesting. I will look into that.

Could just be bad gas.


Has it flooded? Take the plug out and crank to get gas out of cylinder space and put plug back in… crank.

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Could be moisture issues during winter (bad gas)… before pulling it apart, dump a fuel cleaner like ‘starbrite’ into the empty tank, then fill it with fresh gas & run it at full throttle… it may clear the congestion

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I will try all of the following and let everyone know how it runs.


Put StaBil in your tank and run it for 10 minutes or so before storing.


Seafoam will be your friend during this troublesome time.


Or Berryman’s. Either one is great

I definitely would get them valves checked like @SurfaceTherapy suggests and have your coil checked and buy a can of seafoam and get it through the system to eat up all the yellow corn fuel. Oh and make sure your spark plug gap is correctly.

This picture was taken last night. I treated a gas can with Star Tron fuel treatment last fall. It’s a clear as kerosene which normally isn’t the case with 6 month old gas. It’s definitely worth using if you’re not gonna take the time to run Sea Foam in the carb before shutting down for winter. Carbs are too finicky with their small ports nowadays to not do anything and let ethanol gas sit all winter.


Best thing to do is run non-ethanol gas. I run 91 in every gas motor we own.


Just to clarify just because it’s 91 doesn’t mean it’s ethanol free. Here’s a map where you can find an ethanol free gas station. They are far and few between nowadays. Our local Casey’s in our small town use to carry it but longer does. I’ve got a place about 6 miles from my house. I use it in all my tiny carbs like on chainsaws but I don’t worry about it so much in my fuel injected Kohler on my Hydromax. Gas never sits in that thing anyways.



I use that site all the time when we’re traveling in the wife’s car. Nearly all of the 91 near me is ethanol free.

Closest place for me is 30 minutes away…in the middle of nowhere. :cry:

And I drive by 40-50 gas stations to get there. No joke.

That’s rough. If you have marinas nearby they almost exclusively sell ethanol free in my experience. Boats sit more than they’re used. Or buy a 100gal fuel tank and go fill it up and store it at the house.

That’s a good idea. There is one marina but it’s only for residents. It’s worth checking into though.
I called around awhile back to different gas stations throughout my county and the county next to me. Nothing. I think Missouri passed a law awhile back about ethanol in gas.

As in there has to be ethanol in gas?

Yep. Pretty crazy. Especially since Missouri is usually conservative on stuff like that.