Sheridan Model B Sporter

[jirushi]

The A works well again, although it has a slow leak (valve with 6 pumps in was empty the next morning). I have decided that this is not relevant; for shooting, the leak is not fast enough to cause inconsistency. I think it comes from the threads of the two valve halves. I used one layer of 1 mm ptfe tape. A tight fit, but perhaps I should have used a second layer. It is also possible that the inlet valve still leaks a bit, but I cannot hear it.

After adjusting the pump rod (increasing length), so that the pump arm cams over, I am now getting 699 ft/s with 13.73 gr JSB, at 8 pumps. That is quite a bit more than before. Luckily I live in Holland (no power restrictions here).

Cheers

Finding the right length of the pump rod; adjust, test, adjust, test. Until it cams over, but not too much. I used a pin punch instead of the original pin, for ease

[Lawrie Amatruda]

The A works well again, although it has a slow leak (valve with 6 pumps in was empty the next morning). I have decided that this is not relevant; for shooting, the leak is not fast enough to cause inconsistency. I think it comes from the threads of the two valve halves. I used one layer of 1 mm ptfe tape. A tight fit, but perhaps I should have used a second layer. It is also possible that the inlet valve still leaks a bit, but I cannot hear it.

After adjusting the pump rod (increasing length), so that the pump arm cams over, I am now getting 699 ft/s with 13.73 gr JSB, at 8 pumps. That is quite a bit more than before. Luckily I live in Holland (no power restrictions here).

Cheers

Finding the right length of the pump rod; adjust, test, adjust, test. Until it cams over, but not too much. I used a pin punch instead of the original pin, for ease

Hi Louis,

You should use an "O" ring instead of PTFE tape, In my opinion using PTFE is never a way to go when sealing air guns.

Cheers, Lawrie

[jirushi]

Hi Louis,

You should use an "O" ring instead of PTFE tape, In my opinion using PTFE is never a way to go when sealing air guns.

Cheers, Lawrie

Thank you Lawrie, that's good advice.

Would the o-ring just be squeezed tight between the two valve halves?

Many thanks, Louis

[ratbuster2240]

Great fix, fingers crossed it beds in and seals for longer. At least you can use it and enjoy it.

[jirushi]

Thank you James.
Unfortunately, I cheered too quickly.
After about 40 excellent shots, velocity dropped a bit.
A few shots later, I could hear a leak from the inlet valve again.
I should send the valve to a specialist (aka Lawrie or UJ Backus) but this is a bit scary;
if it gets lost...
Another option would be to ask my gunsmith if he can help.
He could probably resurface the nylon inlet seal in his lathe, or make a new seal (delrin, following Lawrie’s advice).
To be continued...

[45flint]

Though I’m impressed with your skills and courage in the end your just convincing me to stay away from this classic American treasure. The strong lock-tight seal says to me Sheridan only wanted these repaired at the factory? Crosmans though not as nicely made are pretty easily resealed. But moreover I just think pump guns are just a inferior design compared to good spring guns? Much more complex, having to hold the pressure, the seal must be perfect and pumping is really inefficient given so much energy is lost to heat.

[jirushi]

"Old thread revival".

My A is working well. My nylon valve seal polishing seems to have worked in the end. Perhaps it needed some "bedding in". Now it consistently holds air; I test up to 8 pumps.
Polishing the inlet seal of the valve, has eliminated the small leak that was present from the start, after the first pump.

@45flint, I think that these valves aren't too difficult to work on, to be honest.
The nylon seals have lots of "meat", so it makes me actually confident that I can keep using it for a long time.
With valves that need a new polyurethane seal, this is more difficult; I would need to buy a lathe, learn how to use it, get rods of polyurethane, and develop skills. This would take years (and lots of phone calls to Lawrie LOL).

Pump guns an inferior design compared to good spring guns?
"Each to their own". My HW30 Lochschaft is probably my best airgun, but I find it boring . I would much rather do a session with say.... my Super Grade

Then the B, which I repaired for my friend Milo.
It is working well and his pride an joy.
Milo has built up this impressive Sheridan collection in the course of only 1 year, and is still going strong. Holland was one of Sheridan's main export markets in the seventies and eighties.