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Stihl 011 runs but only for 30 seconds or so.

bretts

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As above.
I am working on a Stihl 011, it has brand new fuel and vent lines from the dealer, the vent line I can suck air through it and the metal pipe in the tank I can blow air through it.
Carb has been cleaned, adjusted and the needle valve lever is adjusted correctly, the diaphragm etc are pliable (the carb worked on another 011).
The compression is good, the exhaust is clear, piston looks good through exhaust port, air cleaner has both been fitted and removed to see if that makes a difference as has fuel filter.
The reed valve seals properly (the complete reed block also worked in the other 011), the intake gaskets are good and the impulse hole is clear. Three different spark plugs have been tried and all had fat blue spark.
I can get the saw to pop on choke, choke off and I can get saw started where it takes a bit to get started until it idles clean for a few seconds then dies.
I repeat the procedure, choke on, pull until pops, choke off, pull until pop, stumbles, dies, pull again until pop, stumbles, dies, pull again then starts (some times more pulls sometimes less), won't idle for long. Can also introduce fuel directly into carb throat with same results.
Repeat above procedure and this time feather the throttle until saw revs up and hold revs steady until saw dies (also tried to feather throttle when engine revs die down but saw dies). Almost like it's not getting fuel, saw will rev up but not hold idle.
Carb has been adjusted one turn out both high/low needles and one and one half turns out (even two turns out and less than one turn in) with no change.
Pressure and vacuum test has not been carried out at this stage (need to make block off plates and yes yes I need to do this test, please don't bang on about it), carb cleaner spray directed at seals, cyl gasket makes no change to engine running.
What am I missing?.
 

Woodwackr

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May have sucked something into the carb doing all the changes.
Disassemble the carb including needles. If you have a sonic tank, run it in carb cleaner. I use Berrymans, not their spray can…
Gently blow dry. Reassemble. Vac and pressure test. Try it again.
Sounds like fuel blockage inside the carb.
Even with oe fuel line, check for a weak spot that might be collapsing.
 

countryhog

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Look at placement of fuel pump diaphragm. If its not against carb its not installed correctly. Just figured that out, with lots of help, on my poulan 2000
 

bretts

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Found it!.

Fuel filter!.

As a last resort I purchased a brand new oem fuel filter from the dealer and fitted it.
Saw now runs properly.
The old filter looked ok visually and had no restriction when I sucked through it so I don't know what it's deal was.
 
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