Author Topic: Husqvarna 394xp carb issues  (Read 753 times)

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Offline huskyman

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Husqvarna 394xp carb issues
« on: February 21, 2012, 12:22:47 am »

Hello everyone I have a Husky 394 and I just rebuilt the carb with a new kit. The carb is flooding from the pressure of the fuel tank. The inlet needle has been adjusted but this carb is still flooding real bad the fuel fills up the air filter flange and cylinder. Any suggestions? ???

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Offline 660magnum

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Re: Husqvarna 394xp carb issues
« Reply #1 on: February 21, 2012, 07:55:14 am »
The needle and seat valve of the metering valve is not seating and holding pressure. In other words - there is no "pop off" because the metering valve will not hold.

Something is wrong about the assembly?

Missing spring from under diaphragm?
Wrong parts?
Assembled wrong between diaphragm -walking beam - needle?
Adjustment problem ?
Missing Welsh plug?
Leaking around valve seat?
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Offline 660magnum

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Re: Husqvarna 394xp carb issues
« Reply #2 on: February 21, 2012, 09:18:21 am »
You can check if the metering valve holds with the carb off the engine by putting a little pressure on the fuel inlet of the carb.

The metering valve should hold back close to 15 psi pressure or more.

It should re-seat after opening by down to 10 psi pressure

This is called the pop - off  pressure check.

The fuel pump side of the carb can make somewhere close to 7-8 psi fuel pressure and the metering valve has to be able to hold back this pressure if there is no vacuum through the carb.

The actual function of the metering valve is to act as a demand regulator for fuel delivery for the engine. It is to remain closed unless there is a vacuum signal from the engine that it is running. This vacuum signal can be developed by pure intake vacuum when you choke the engine or it can be developed by venturi vacuum when the engine is spinning faster.

It is supposed to take a about 4" wc vacuum on the underside of the diaphragm to open the valve but there is not a simple to apply this or check the actual vacuum as it to do the pop - off pressure on the fuel inlet of the carb.
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Offline huskyman

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Re: Husqvarna 394xp carb issues
« Reply #3 on: February 21, 2012, 12:41:14 pm »
Ok thanks do you think it could be the tank vent being plugged?

Offline mweba

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Re: Husqvarna 394xp carb issues
« Reply #4 on: February 21, 2012, 12:56:01 pm »
Run it with the cap **** open a bit.  If that fixes it, tank vent it is.

Offline 660magnum

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Re: Husqvarna 394xp carb issues
« Reply #5 on: February 21, 2012, 01:29:32 pm »
When you assemble a carb

On the pump side, The diaphragm goes against the main body and then the gasket and cover.

On the metering valve side, The gasket goes on first and then the diaphragm and cover. If this is done backwards, it will hold the metering valve open and fuel will go right through the carb.
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