Tree down, and now chainsaw refuses to run under throttle for more than a minute

Had a tree go down on the corner of the property about a week ago. Not in a critical area, but it fell just behind the gate that gives access to my supplementary parking area, so I do need to get it cleared. Went out to do so today, and now my chainsaw is acting up. Shindaiwa 415, was gone through by a shop maybe two years ago and has seen little use since. Fresh gas. Starts fine, and will idle seemingly indefinitely, but once I give it throttle it revs up for a few seconds, then dies. Feels very much like it's running out of fuel.

So far, I've checked air filter (OK, and no change with it removed entirely), fuel filter (looks new), fuel lines (pliable, not gummy, blown out with compressed air), carb (clean and shiny), linkage (working properly), spark plug (gapped properly and just a little sooty - normal for 2-stroke, IMO), and spark arrestor (clear). Where should I look next, other than to buy an electric (and don't think I'm not considering it)?

Fuel pickup tube inside the tank.  Does it have the weighted filter on the end so it will stay down in the fuel when you tilt saw?

Some saws have a check valve in the fuel cap or the line that can clog. 

In reply to 02Pilot :

Can you see the fuel line in the tank?  Does it look OK? The fuel line on my brush cutter rotted through near the top of the line and gave me symptoms similar to what you're describing.  Also earlier this year I learned that TruFuel (i.e. no ethanol pre-mix) is garbage, my leaf blower ran much better once I drained it out and replaced it with regular ethanol gas and two cycle oil. 
 

I recently went electric to a Milwaukee M18 and haven't regretted it. Batteries are expensive, though, and it depends on how long you're cutting at a time. 

Main jet in the carburetor is gummed up.  Take the carb apart and clean it.

I fished the fuel filter out of the tank. It is weighted and appears virtually new. The line was pliable and showed no signs of failure. There's no check valve in the cap; there is a rudimentary tank vent (basically a rubber plug with a convoluted passage to let air in) that seems to be clear. I used fresh gas from the local Sunoco plus a can of 2-cycle oil. I have not pulled the carb apart, but it seems the next logical step.

I have a Ryobi 40V snow blower, so I could just get one of their bare tools and use the batteries I already have. Very tempting at this point, but I also refuse to be defeated by something this simple.

In reply to 02Pilot :

Before you tear into the carb, spray it with some carb cleaner and let it idle. My old Stihl was running badly and this corrected the issue. 

In reply to rustybugkiller :

I'll second this. With both my string trimmer and pit bike I've actually just sprayed cleaner in the carb, let it sit for a while and it cleans it enough to run normally.

My small Stihl got to running pretty crappy.  I cleaned out the spark arrester screen in the muffler and it ran like a dream after that.  I have only ever used no alcohol gas in it from new.  

Pulled the carb. It's spotless, no blockages.

I've got the Ryobi 18" electric chainsaw and I won't go back.  And, yes, I have other Ryobi stuff that share the batteries.  The last chainsaw was 2 stroke and whenever I went to use it, it seemed to have a different problem every time.

In reply to triumph7 :

Well, it's good to hear a recommendation for the Ryobi electric.

In reply to 02Pilot :

was the fuel metering diaphragm rigid or flexible? 

If its not flexible, it cant "pump" fuel right. 
 

triumph7 said:

I've got the Ryobi 18" electric chainsaw and I won't go back.  And, yes, I have other Ryobi stuff that share the batteries.  The last chainsaw was 2 stroke and whenever I went to use it, it seemed to have a different problem every time.

I have a dewalt electric for the same reason. I only need the saw a few times a year, and there was always an issue, most like the one you're having. Grab whatever one you already have batteries for and it's always ready when you need it

Try a little choke to see if it improves.  That will tell you if it is running lean.   But yes electric really is the way to go for small tools now.  Wish my neighbor would get the message, he seems to run a gas motor for half an hour once a week, even in winter when there is no reason.

Check to make sure your primer bulb isn't cracked.  Had a string trimmer that would run 1/2-3/4 throttle but stall if you ran WOT for more than 5 seconds.  Primer bulb was cracked ever so slightly so it would not keep prime under full load.  

In reply to jmabarone :

Had the opposite problem on my husqvarna.  Primer bulb had weakened and not cracked.   As soon as there was fuel demand, it collapsed and somehow prevented fuel flow.  Would idle ok, but ask for throttle and it would sputter and die.