Stalls and won't start back up.

[Bricknose]

So I have a Craftsman 3.3 (Poulan 3300) chainsaw that I recently picked up. I have no history on the saw but it allegedly ran fine last winter. The issue I am having is that it will start up just fine when it's cold, but after about five minutes it stalls out and won't start back up, I sometimes get a little putter, or it will even run for a second or two, but it usually just pulls and gives me nothing. It usually takes almost a day before it will run again.
Fuel is properly mixed at 40:1, carb is clean and it is getting fuel. there is no pressure building up in the gas tank, so I don't think I have vapor-lock. There is a consistent, blue, spark. The plug is new and gapped to 0.025", and the coil air gap is 0.012". Air filter and spark arrestor are both clean and clear. I fpulled the flywheel and the key is not sheared, and the magnet is still strong. Compression for the motor is 130psi, and I inspected the cylinder to find the original crosshatching still present, no major scoring.
I have no excessive smoke and the spark plug is never wet, so I don't believe it is flooding, but I tried following the directions for starting a flooded engine anyways, still to no avail. A few nights ago I decided to spray a bit of carb cleaner throught the intake of the carb (I know, Its bad for the engine) but I got one little put from that and that was it, I tried a second time and got absolutely nothing. Which makes me thing it is more ignition related. The spark looks fine outside, but I have no idea how good it is when under compression.
I disassembled and cleaned out the carb, and set the idle and mixture screws to 1 1/4 turns out, which is what the service manual said to use for a fresh rebuild before initial tuning, but I can't get it to run long enough to make any adjustments to it.
So I guess I'm just looking for some advice on where to go next with my diag process.

 

[Bob Hedgecutter]

First off- well done- good description of the process of elimination thus far and steps that have been taken.
First thoughts were as dying coil, but you still have good spark once the saw stops- so I would be suggesting not flooding, but a lack of fuel entering the combustion chamber might be your problem.
Things like clogged fuel filter, soft fuel line collapsing flat under vacuum suction, clogged mesh screen within the carb, faulty and sticking needle valve.
If possible, stripped carb cleaned in an ultra sonic cleaner is about the best resurrection- followed by correct reassembly with an OEM rebuild kit, new fuel line and new filter.
If everything else checks out, lack of fuel supply is about all it can be.
Rather than carb cleaner- try a teaspoon full of mix directly down the carb throat (remove air filter) with the choke open to allow the mix straight down the intake tract and try to get the saw to fire on that- if that does not work, it might be something to do with the ignition or rather the ignition stopper- faults to earth in the kill switch or its wiring.

 

[Scott kunz]

Spark needs to be able to jump 1/4” gap. Using a spark plug isn’t the best way. A tester that you can adjust the gap is best

 

[Bricknose]

Alright, thanks for all the advice so far, I'll recheck the spark with an adjustable tester, and I did find an OEM rebuild kit for the carb, so I'll take that apart again, the diaphragm and needle valve didn't look bad, but I have no idea how old they are and they did sit with old fuel for a while, so the diaphragm might have hardened just a little bit too much.The fuel line and filter were replaced when I first got the saw, the old one was rock hard and broke apart when I tried to unhook it from the carb.

 

[Bob Hedgecutter]

Alright, thanks for all the advice so far, I'll recheck the spark with an adjustable tester, and I did find an OEM rebuild kit for the carb, so I'll take that apart again, the diaphragm and needle valve didn't look bad, but I have no idea how old they are and they did sit with old fuel for a while, so the diaphragm might have hardened just a little bit too much.The fuel line and filter were replaced when I first got the saw, the old one was rock hard and broke apart when I tried to unhook it from the carb.

If the saw stops running and you do the spark test for dummies (which is mostly all I ever rely on) with the plug out and earthed to cylinder to see a visible spark, I would call it good. If you want to be extra sure open the electrode gap to near double what it should be, if you still get spark then all is good for sure.
Could be the mesh screen inside the carb- old fuel can leave that covered in dry varnish when the saw sits a long time- it looks good visually but is actually varnish sealed.
Mix down the carb throat will help prove or disprove that one.

 

[Bricknose]

Well I got the saw out again today, and after it stalled, I poured a little bit of fuel down the intake, and after a few pulls it did start back up and run for a few minutes. So hopefully a proper carb rebuild will be all I need.

 

[Bricknose]

Alright, so I overhauled the carb with a Walbro kit, and I checked spark with a plug gaped to 0.1". I found a little bit of dirt behind the small brass cup plug, and spark was still strong and blue across the large gaped plug. After reassembly, I had no change. It ran for a few minutes and then stalled, refusing to start back up. Earlier today I started to look at it again and found a break in the hose running from the crankcase to the carb, so it wasn't pumping fuel. I replaced that line and now it starts and stays running (for the most part) and I can always start it up after turning it off. So the main problem is fixed, although I think it's weird that it ran at all with that line broken the way it was.
It still takes a few tries to start it, it idles a little bit low, and shows signs of running really rich. So I should be able to take care of all that by tuning the carb. I know that I would want to have a bar and chain installed when I set idle speed, but its it necessary to have a bar and chain when adjusting the low and high speed fuel mixtures? With low speed, it shouldnt be moving the chain anyways, so I wouldn't imagine it matters, but with high speed adjustment, I would imagine that being under the load of spinning a chain would ever so slightly effect what mixture would be ideal.

 

[Bob Hedgecutter]

So we were on the right track- fault in the fuel delivery.
Filter and fuel line were my next stop if all else checked out, but you beat me to it.

Tuning as far as I am concerned, is done as the saw would be run- so complete bar and chain, plus all air filtering and air box covers in place.
Idle to where the saw keeps running but hopefully not spinning chain, low circuit to peak revs then backed off a little to give good throttle response, idle reset to bring the chain to rest, high circuit to peak at full throttle then backed off to 4 stroke a little and clean up when the saw is under load cutting wood.