I just added to my post above about the single exhaust port valve vs the multiport one. Which do you have? The single port must be in the right way or you cant start the nut without breaking off the tab and the port will not be lined up. The multi can go in any way.
If you are using two new lead seals they can be hard to compress enough to start the nut. Try leaving out the lead seal under the nut. If the nut starts then crank it down to see if it will compress the valve seal enough to make it start then add the second seal under the nut. I had to use the TEF rope I mentioned above under the nut on one gun when i could not get the lead one to compress enough to start the nut when using both lead seals. It is easier to compress than lead. If Mac1 is still working on getting back open he has thiner flat white TEF seals for those locations that work so much better than lead for me. I used them on two other guns and the nuts started so easy.
Quote from: Van on May 14, 2025, 10:40:40 PMIf you are using two new lead seals they can be hard to compress enough to start the nut. Try leaving out the lead seal under the nut. If the nut starts then crank it down to see if it will compress the valve seal enough to make it start then add the second seal under the nut. I had to use the TEF rope I mentioned above under the nut on one gun when i could not get the lead one to compress enough to start the nut when using both lead seals. It is easier to compress than lead. If Mac1 is still working on getting back open he has thiner flat white TEF seals for those locations that work so much better than lead for me. I used them on two other guns and the nuts started so easy.Only the rear washer is lead. The front that mates to the inside surface is a flat rubber ring. I was pondering if perhaps the tip of the exhaust valve is not fully seating into the opening of the spring. That would certainly be enough space to keep the threads from starting on the nut. I wonder if that has ever happened to anyone before?
Quote from: sweatyk on May 15, 2025, 04:13:03 PMQuote from: Van on May 14, 2025, 10:40:40 PMIf you are using two new lead seals they can be hard to compress enough to start the nut. Try leaving out the lead seal under the nut. If the nut starts then crank it down to see if it will compress the valve seal enough to make it start then add the second seal under the nut. I had to use the TEF rope I mentioned above under the nut on one gun when i could not get the lead one to compress enough to start the nut when using both lead seals. It is easier to compress than lead. If Mac1 is still working on getting back open he has thiner flat white TEF seals for those locations that work so much better than lead for me. I used them on two other guns and the nuts started so easy.Only the rear washer is lead. The front that mates to the inside surface is a flat rubber ring. I was pondering if perhaps the tip of the exhaust valve is not fully seating into the opening of the spring. That would certainly be enough space to keep the threads from starting on the nut. I wonder if that has ever happened to anyone before? If your gun is an older one It used an exhaust valve with a 5/32'' diameter raised boss that seats into a spring of that size opening. The later "C" guns used a 1/4" boss and fit in a spring with a larger spring opening. A later valve would not seat into an early spring if mismatched. Thats the only thing I can think of to keep it from fully seating.
Here is a photo of the assembly page from the repair manual stating to leave out the lead seal under the nut with everything else in place including the seal under the valve and only use that seal under the nut if you get blowback when fired. If the nut tightens down and no blowback you may not have to have that seal. One of the seals may be too thick for the nut to catch.
JG Airgun has a list of Sheridan serial numbers that I have printed. 1977 went from 175840-211020 so it falls in that year.
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