Stihl 440

[*tedd*]

Anyway.....different subject.
Can anyone solve a saw problem for me? I have an 044 with gas poring out of the carb (Back preasure!). I have put two pistons and cylinders on it (last one, brand new Stihl OEM). Runs great until I shut it off and after it sits for a while the case fills up with fuel until it pours out the carb. I've put at least three different carbs on it. If I wasn't bald already, I'd pull out the rest of my hair!

 

[Jacob J.]

Inlet needle lever set to the correct height? Fresh metering diaphragm/carb kit? Debris keeping the inlet needle from seating?

 

[Martinm210]

Yeah, I second the carb needle.

Buy a walbro HD kit if that's the carb you've got and install it. They are only a few bucks and most dealers carry those in stock.

You could try to just pull the carb apart and clean it, but I find it hard to keep the gaskets in good shape without tearing apart. Besides, the carb kit is so cheap, while you're in there...you may as well replace those diaphrams, the needle, screens, etc...they are really easy to install..

 

[*tedd*]

Thanks guys but, I've already done that, I've tried every trick I can think of and I do this for a living!

Life's journey is not to arrive at the grave safely in a well preserved body, but rather to skid in sidwayes, totally worn out , shouting "Holy $hit...What a ride!

 

[Jacob J.]

Well then you know as well as anyone that this is carb related. Something has to be happening to allow fuel to go through the carb while the saw is sitting. Are you using Walbro HDs and do they have the nylon one-way check valves in place? Is the fuel pump diaphragm right up against the body of the carburetor? There is no other way your crankcase can fill with fuel unless a Smurf got in there and installed a tube directly from the fuel tank to the crankcase.

Another thought- if you got these carbs off old timber falling/landing saws- then it's possible the inlet needle seat is worn so far down that the lever won't have room enough to let the needle seat properly. I've seen that happen in HD carbs. The lever hits the body of the carb and keeps the needle just slightly open. Check that out.

 

[TheRickster]

Also chack the tank vent to be sure it is open. Could be pressurizing the tank when it get s some heat in it..

Rick

 

[Lakeside53]

Any tank pressure is fine and wonlt pop-off a correctly adjusted and seated inlet valve.... and is advantageous for starting. Newer vent systems are all "one way".

Just disconnect the fuel filter and pressure test the carb. You may well have a bad seat.