Chainsaw Repair

I'm on a run of leaking carb. needle valves.  Got 4-5 apart now won't hold pressure.  Had a few with rubber tip they won't hold either.  Carbs have been through ultrasonic cleaner.  Any redneck fix for the seats?  Seems I remember toothpaste to lap???  If so how do you?
Shep

Thanks for the confirmation on the toothpaste.
Shep

I've seen it a lot lately where it will be the upper flapper diaphragm that will be bleeding the pressure off.  I don't know if they get a little pin hole or if the cover gets warped but they bleed down when testing the pop-off pressure.  You can put grease on the needle and hold it down with your finger and the carb will still bleed pressure.  It seems to happen more on carbs with one screw holding the top cover down.  Most of the time a new flapper and gasket will take care of it.

He's probabley refering to the fuel pump check valve assembley .FWIW the soft parts of the carb just get stiff from old age or ethanol .There's nothing you can  do except replace them .

I've probabley rebuilt in excess of 100 saw carbs and never once seated a fuel shut off valve .Fact I've seldom ever replaced them .I seldom even buy the complete rebuild kits ,usually just the basic kit with the soft parts .