Honda GX390 erratic running at full throttle - Snowblower Forum : Snow Blower Forums
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post #1 of 17 Old 12-20-2017, 05:38 PM Thread Starter
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Honda GX390 erratic running at full throttle

I have a honda GX390 on an Ariens 926LE. The motor is near brand new. When I used the snowblower last week, it was working ok but today when I started the motor it was not working smoothlly. At full throttle, the revolution goes high-low-high-low... It is like the tank was getting empty. I see the governor going from one side to the other side. Do you know what could be the problem ? Air filter is dry. Thanks.
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post #2 of 17 Old 12-20-2017, 05:46 PM
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Fuel valve turned all the way on?
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post #3 of 17 Old 12-20-2017, 06:07 PM Thread Starter
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Fuel valve turned all the way on?
Yes
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post #4 of 17 Old 12-20-2017, 06:16 PM
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it's hunting because it is starving for fuel. most likely the pilot jet got clogged by a little dirt. i would take bowl off after shutting fuel off, drain gas from bowl first from 10mm nut on side of bowl.

spray carb cleaner up pick up tube and all around.

then take pilot jet out. it is on top side of carb facing out. you have to unscrew that throttle stop screw out first. then gently pry out pilot jet with small screwdriver. clean jet and inspect that small 0-ring on jet. clean the jet out with carb spray and dry with compressed air if you have that. i use a can of air from costco that people use on computer keyboards.

also spray cleaner down hole where pilot jet goes. then put a little oil on o-ring before installing o-ring and make sure it goes all the way in. it should pop back in.

even though it is a new engine, this happens all the time. just takes a microscopic piece of dirt to mess up the carb. maybe from old gas or dirt in gas tank. eyeball the gas tank. you may have to flush out and change fuel filter.

there are a couple good videos on you tube on doing this for surging or hunting Honda carbs.

this usually works for me.

good luck and check back.

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post #5 of 17 Old 12-20-2017, 09:56 PM Thread Starter
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Could it be due to carburetor icing ?
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post #6 of 17 Old 12-20-2017, 10:46 PM
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I’m assuming you used a general purpose gx390. Did you remove the air Filter? Try without.

Somethings going on with the fuel air mixture. Could also be a clogged jet.

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post #7 of 17 Old 12-20-2017, 10:48 PM
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Is it right after a cold start with rpm surging? Try leaving choke out just a 1/4 way while it warms up. Then cut the choke out all together once it gets under load.
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post #8 of 17 Old 12-21-2017, 10:39 AM
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Quote:
Originally Posted by vmax29 View Post
Is it right after a cold start with rpm surging? Try leaving choke out just a 1/4 way while it warms up. Then cut the choke out all together once it gets under load.
exactly what i should have suggested first. if it will only run right with some choke engaged then the carb needs to be cleaned, especially the jets and the emulsion tube.

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post #9 of 17 Old 12-23-2017, 03:30 PM Thread Starter
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I started it today. When the motor was warm with the choke used just a little bit, the motor ran smoothly. The standard main jet in a GX390 is a #95 on the Honda HS1332, which have a winterized gx390, they use a #102.
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post #10 of 17 Old 12-23-2017, 05:07 PM
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Sounds like you got it figured out! Good deal.
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