Red Max Back Pack Blower

I sent in a post earlier on a "no fire" issue with a Red Max back pack blower. I installed a new igniter and fixed the "no fire" It starts and runs fine until it revs up to about half throttle. At that point the engine acts as though it is starving for fuel and unless I back off the throttle, the engine will die. It starts back up ok but more than half throttle the issue starts all over again. I have cleaned the fuel filter, and tried it without the filter. (no difference) I replaced both fuel lines, and cleaned the exhaust port. (it was not that dirty) I ran it with the muffler off, no difference. The carburetor is apart on the bench, and the diaphragm works well on priming. No visable dirt or gum in the carb. I suppose there is an adjustment for the spring on the feed that the diaphragm pushes against to pump fuel but I do not know what that is as I don't have manual for this machine. What have I missed, or should I just replace the diaphragm and see what that does?

 

Something is restricting fuel flow in the carb. If the diaphragm is soft and flexible it should be fine. Does this have mixture screws to adjust?

 

No adjustment screws on this carb. I could probably drown this carb in cleaner but that is about all I could do from what I can see. I have seen diaphragms in better condition, but this one pumps fine with the primer button. I'm really scratching my head on this one.

 

If you think it might be bad, it probably is. The primer working or not has little to do with the diaphragm or determining it's condition.