Pressure/Vac Test Sealing?

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Pull 15 inches of Mercury, if you pull 7.5 vacuum, that about 3 psi. Too low.
You are right! The MightyVac MV8500 scale is PSI on the pressure side and inHg on the vacuum side--thank you!

Decomps will almost always leak at 7 inches of vacuum. Usually pulling out on them slightly will seal it off. 👍
Thanks for the tip. Pulling on it helped, turning it several rotations seems to have "lapped" the surfaces or at least cleaned it up better than I did (and I got it "clean" from what I saw). It now seals well so I won't use it so it doesn't carbon up (probably doesn't matter much in the big picture).
 
I have a box of scraps that I use for this - generally pieces of rubber inner tube next to the muffler/cylinder, then a thin piece of metal and finally a block of wood. All with two holes drilled in them to fit the existing bolts. Every saw seems to require a slightly different setup. I sometimes us a sash clamp to hold it all together. I generally send air through the impulse line and submerge the saw under water. Dry the saw off and repeat out of the water for vacuum.
 
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