Author Topic: 394XP wonít stay running/barely starts  (Read 529 times)

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Offline Tbe2018

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394XP wonít stay running/barely starts
« on: July 03, 2018, 08:03:21 pm »
 Hello all,

I am at a complete loss-  my Husqvarna 394 chainsaw will start but immediately dies. It is a 1998 model.

I have already tried the following:

New Gas line
New Fuel filter
New Fuel tank vent
New tank vent filter
New Gas cap
Put carb kit in it
Cleaned the carb
Air filter is clean
Spark plug gap is fine - to specs
New spark plug
Gets spark
Decent engine compression, according to the shop (120)
Muffler is clean
New gasket between carb and intake opening

Took it to the shop and they said it isnít getting enough fuel (hence the overhaul of the fuel system I did) and wanted to charge me $150-200 to figure out the problem and fix it so I said ďto hell with it, I can do thisĒ- but Iím starting to give up.

I tried adjusting the L needle on the carb multiple times (started with it 1-1.5 turns out as the manual suggested), but it wonít stay running long enough to make the adjustments. The metering lever is set to just about level with the carb body. It is a Walbro wj70 806 carburetor.

The problem seems to intensify when Iíve been trying to start it for a while - aka when the engine is hotter. It usually always starts with the choke on and sometimes even stays running longer -a few seconds longer- (revving high of course ) until the choke is pushed in and it dies. Also, the decompression valve doesnít always pop out even after it ran for a couple seconds. Took that out too and cleaned it, seems to be functioning well.

Any and all help would be MUCH appreciated.

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Re: 394XP wonít stay running/barely starts
« Reply #1 on: July 03, 2018, 10:54:45 pm »
I just looked at a weed eater that I thought for sure was a fuel problem and rebuilt the carb and went through it all.

It turned out the crankcase screws were loose and would not allow enough pressure in the crankcase to get it to move fuel up into the combustion chamber.
So I would do a pressure test of the crankcase.   It could be the crank seals or a leak around the gasket where the crankcase comes together. 
Also you need to check the intake itself and make sure it is tight with no cracks or splits anywhere.
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Offline Cut4fun .

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Re: 394XP wonít stay running/barely starts
« Reply #2 on: July 04, 2018, 08:14:36 am »
Getting hotter and worse tends to lean toward seals.

But also while going through it.

Have you looked at the piston rings yourself?  120 to me is getting borderline.
If not pull muffler for a look as you could have a ring stuck. Could be hidden from few too. Been there done that.


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