GX390/420 fuel tank, second hose

theoldwizard1

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Sep 9, 2012
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I have acquired a pressure washer with a GX390/420 (says 15hp) Honda engine. Besides the main fuel running from the tank to the carburetor inlet, there is a second smaller hose that runs from about 3/4 of the way up the tank to the intake above the carburetor. This looks like some kind of a vent hose, but it you fill the tank up above that level fuel run straight into the engine !

What is it purpose and how do you prevent the fuel from a full tank from running into engine and causing it to hydro-lock ?

Looking at various pictures of these engines (and clones) some have this hose and some do not.
 

Notdumasilook

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Oct 16, 2018
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You have me baffled. I have a 390 genny and it has only 1 fuel line to the carb. Tanks has a separate fuel line/petcock @ back corner of the tank.. and only vent is coming from the valve cover back to the intake. Any way u can post a pic? Question..... does your model have a fuel pump or is it gravity feed? I can picture them routing gas back to the tank from the fuel pump if you have one.

!! Just looked at a photo of the GX390 pressure washer. THAT is a serious machine. Pity is theres only a pic from one angle and cant make out much..
 

SidecarFlip

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Aug 21, 2018
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I have one on my engine as well. I slid the hose up in the tank grommet do just the end is sticking out in the fuel tank. That eliminated it sucking fuel in from a full tank and bogging the motor. I's a tank vent so fuel will flow. Interestingly, the Harbor Freight Predator engines (the bigger ones are exactly the same setup. Have one of those as well and I pulled the hose on that one too. In the case of the Predator engine, the secondary hose goes to a charcoal cannister and then the carb on the vacuum side.

Never had an issue with hydro lock. The motor sputtered to a stop as soon as it got a big gulp of fuel. Just pull the hose up in the grommet and your issue will be eliminated.
 
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