question for a mechanic about a Walbro carb

[ronbourd]

Please can someone tell me what is the minimum pressure  (psi) that the needle valve should  hold before releasing on a Walbro carb , this is when you apply pressure with a tester on the fuel inlet hose.The chainsaw is a 154se Husqvarna.  Thank you for your help! Ronald

[joe_indi]

Minimum pressure not stated but maximum pressure is 14.5psi
Joe

[sharkey]

Joe is correct.  Minimum reset is around 3.5psi, any lower and it will leak.  Try polishing the seat and see if you can get it up over 5.  Older seats that are brass tend to ovalize and once that happens theyre not coming back.

[ZeroJunk]

Interesting, one of the top saw builders has a video about the problems with one particular HDA199 Walbro carb/saw combination and he wants it to hold 15 pounds minimum wet and doesn't care what it is as long as it is minimum 15 pounds.

[smmyb123]

From what I understand, no modern carb should be pressurized above 10psi (.8 bar). It should hold 10psi indefinitely when applying pressure to the fuel inlet. Try pulling vacuum on the jet from the brass plug located under the metering diaphram, if any drop in vacuum then you have a bad check valve.