5 Series carburetor run issues

[Stump Shot]

Some run issues with carbs and what the fixes were.

Problem, saw runs eradic and eventually dies. Also passes a crankcase pressure/vacuum test and is fine mechanically and has good spark.
Leaving the fuel system suspect.
Carburetor passes a standard fuel inlet pressure check.


However, it fails when a light vacuum is applied to the primer outlet, with the inlet blocked off.


Upon disassembly it was found that one of the little flaps on the fuel pump side was lifted up with some crud growing under it on the carburetor body due to the use of ethanol fuel. This allowed a short circuit to the main nozzle, which makes it uncontrollable.
Carburetor was cleaned along with a new gasket and diaphragm kit and reinstalled. Tests were now passed as well as running confirmed saw was back in proper condition.

 

[Stump Shot]

Another start and immediately die situation with direct opposite test results.
Vacuum to the primer outlet side without the aid of blocking the inlet pulled a vacuum, which it shouldn't. This told me that an inlet problem was apparent. Needle and seat checked out, that left the inlet screen, which was found to be plugged with fine debris. A new screen took care of the situation and saw was back in working order.

 

[big_eddy]

I’ve had the latter several times. Saw will idle all day long, but pull the trigger and put it into a log and it dies almost immediately.
Clean the screen and back to normal operation.

 

[Bjorn]

Hello. I find this on youtube.

What is he doing, changing?