husquvarna 136 repair

Is a husquvarna 136 fuel tank suppose to be pressurized or is it vented? I know the tank has a check valve so im not sure how that works, the saw will crank and idle but dies when you give it gas. i bought new carb off ebay instead of cleaning the old one and when i pulled the fuel line off it sprayed all the gas out of the tank so my guess is its supposed to be vented i know stihl saws are vented but all i see is check valve for this saw so is that the vent?







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The fuel tank should run 7 to 10 psi.
This pressure is needed to keep the fuel up to the pump in the carb.
If there is a return line from the carb to the fuel tank then the tank is pressurised.
If there is no return line the tank is not pressurised.
With most stihls the cap is 2 way vented to maintain the pressure head.

If your trimmer starts and idles fine then dies when you throttle up then you either have an obstruction in the high speed circuit or a blockage in the muffler.