Canadian Airgun Forum

I have been having a slow leak for a long time and some o-rings have been changed in the grip reservoir.

I suspect that the problem is with the valve and with the seat that is buried deep in the frame.

The diagrams I have are really not that useful and I cannot find anything online.

Any chance that another member had to disassemble his pistol and could give some guidance?

Thanks.

R-Gun Pete

seams like a very simple enough pistol to work on
if you have trouble Pm me

_________________
"A candle loses nothing by lighting another candle"

If I remember right, the Alfa Proj is a Czech made pistol. It appears to have close similarity to the old BRNO TAU-7 CO2 pistol. I have worked on a few leaking TAU pistols and the remedy might be simple. The TAU seems to share a similar looking Teflon valve seal and steel stem with a tapered seat.

Depressurize pistol. Remove the grip on your Proj by removing the threaded ring (use your spanner tube wrench). Once the grip is off you will see the threaded end plug (#29 - packing bolt). Remove this bolt/plug. Slide out the o-ring (#59), bushing (#48), valve spring (#53), spring guide (#47) and valve stem (#16 -piston). Clean all these parts, especially the stem seat. The stem might get hung up on the seal so you might need to carefully use tweezers or something to carefully pull it out. Once it's out, look down the valve chamber and you will see the Teflon seal (#67). Use a q-tip to clean the seal but leave it in place. Insert the stem. Carefully slide a skinny brass bolt or nylon rod into the chamber to contact the end of the stem. Give a few very gentle hammer taps on the rod to seat the seal using the stem. Sometimes this seal will creep out if the pistol hasn't been used much. Reassemble the rest of the pistol with a drop of lube on the o-ring.

You will likely wreck the Teflon seal (#67) if trying to remove it. Often you can stop the leak by seating the seal (as above). You might have to repeat the procedure if it continues to leak. As a last resort you can pull the seal and replace. Have a good look at the stem while you have it out to be sure there is no rust or gunk (hardened lube) on the tapered seat. My pistol would sometimes leak if a thin lube got to the seal through the exhaust port. Cleaning the seal and stem fixed the problem.

https://www.pyramydair.com/airgun-resou ... manual.pdf

https://www.pyramydair.com/model-schema ... istol/1564

Hi Ace and TC Cooper.

Thanks for your reply. I have the same diagram that you both referenced. It doesn't look too complicated except for the fact that the seat for the valve is deep into the receiver.

It is not very user friendly.

I remember reading somewhere that removing the seat would call for trouble and I didn't touch it at the time so the suggestion from TC Cooper to use the stem and tap it to reseat the seal is worth a try. If I am totally unsuccessful I will P.M. you Ace.

Thanks again.

R-Gun Pete

Please let us know if it helps.

I have one that is leaking.

_________________
Geoff - CAFTA Governor

I did this on my TAU7 after receiving the same advice from Todd. Thanks Todd. It is still sealing well.

_________________
Tim
CAFTA Governor

My TAU-7 leaked when I took it out this summer. It was sitting all winter and I guess the Teflon seal creeped out a bit. I removed the threaded plug, removed the spring, inserted a brass rod and tapped on the stem a few times. Then reassembled and all worked fine so I shot it quite a bit during June and July.

Pulling an unusable or damaged seal is a bit tricky. I did it once before figuring out the seating method. To pull the seal I used a long drywall screw because they have course and deep threads. The screw was carefully hand turned into the seal hole (just a little bit) so I could carefully pull out the seal. The idea worked very well. A probe with a small hook on the end might work too but I like that a screw contacts the seal around the entire hole so you can pull straight out without touching any metal.

I didn't monitor my post yesterday as I was busy trying to fix my Alfa Proj PCP pistol.

After pressurizing the gun, I started by doing a full leak check before disassembly, only to
discover that there was a major one in the bottle (pressure vessel) located under the grips.

I thought this part was repaired as I had worked on it in the past and also the reason why
I thought that it was possibly leaking from the valve seat when I asked the question in my initial post.

I don't remember where I obtain this diagram of the pressure vessel but
I don't think it is easy to find so I will try to post it.

The leak is coming from the joint between part 2 and 1 (Regulator Body Front and Rear ).
The first time I worked on it I didn't noticed that there is a small machined groove in the
mating surface of 1 and this is from there that I could feel the air escaping.

These are the only parts that are fairly easy to disassemble: 7, 2, 9, 6 and 1. I didn' try the other end
because it was not leaking but the flats on part 13 (Male Connector) should provide some grip
to unscrew the intake assembly out.

As to remove part 1 from 12 (Cylinder), I guess they are screwed together but the drawing is not clear
if it is actually threaded but it should be. Being both round and smooth I am not sure on how to seperate them
without damaging them.

Also I am not sure if I should separate them because it is not leaking in that joint. My guess would be
that the defective part is o-ring 9 because it should stop air from coming into the space between 2 and 1.

On the other hand I cannot remove 3 (Piston) from 2 to check o-ring 8
because it is way too thight and I am not able to pull it out.

After changing o-ring 9 twice it is still leaking so maybe the problem is o-ring 8. This means that the
air goes from the valve through the hole in the piston (3) into part 2 where it enters the receiver and
stops there because the valve is closed. Then the pressure builds up and if o-ring 8 is the problem,
the air reached the cavity between 2 and 1 to escape through the small groove.

If it is the case, how should I proceed to remove the piston 3 from regulator body 2?

Thanks.

R-Gun Pete

Exploded View


Close up of Regulator

I forgot to add another thing to my previous entry. If I cannot remove the piston I was thinking that I could add a thin rubber gasket between 2 and 1 to prevent air from going in the groove.

On the other hand this groove is probably a safety feature so I guess it might be not so great an idea. What do you think?

R-Gun Pete

It looks like #2 and #3 are just held together with o-ring #8 friction. Maybe the o-ring has degraded and is stuck to the parts. I'm guessing these parts are aluminum so you will have to be careful not to damage. No pliers.

Is it possible to use a rod through the top end of #2 to gently push #3 out? A nylon rod should be okay.
You could try putting #2 and #3 in your freezer for a few hours. That might make the o-ring brittle enough to let go.
You could try some lube and let it soak.
A heatgun might be enough to get the seal to let go. Try low heat first

I am grateful for TC Cooper suggestions as they got me going instead of continuing to be stuck in a rut as before.

One part is aluminum and the other is brass so I thought the easiest thing would be to start with heat. After getting them toasty I tried to pull them apart with gloved hand but even with feeling the heat through the gloves the parts didn't budge.

The hole being too small to push from the inside meant that the components must come apart by pulling. Looking at the brass piston and its small o-ring groove gave me the idea of making a plate that would hook in the groove to give me more pulling lever. I had a piece of soft aluminum for shearing, it doesn't machine very well as it is gummy but I just needed a crude tool. For the aluminum regulator body, I drilled a 5/8 in. hole in a piece of hardwood flooring board. Those two tools combined with a few wooden wedges should do the job.

The bar being very soft, the wedges started to push the ends up without pulling the piston. I wanted to push the ends down to straighten the bar and at some point I started to feel something moving so I continued pushing on both ends until the middle was bent up and the piston was out.



I then discovered that the o-ring was hard and crumbly which seems a very likely source for my leaking problem.

After re-installing new o-rings, the pressure vessel was re-assembled and a pumping to 200 bars seems to confirm that the leak is gone.

Tomorrow will tell if the pistol is holding the pressure but I am more confident than I was previously that the case is solved.

Thanks again.

R-Gun Pete

Yeeaaahhhh... the o-ring lost the battle! Nice work! Maybe you could post a pic of your assembled pistol?

there you go
congrats easy peasy...

_________________
"A candle loses nothing by lighting another candle"

Its seems that my Alfa Proj pistol is cured and in good health now.

After no air loss overnight, I did a quick shot count test in my garage. It was around 10 degrees C but I don't think it should have any impact on the shot count.

I reached 112 shots before the residual air was dumped and it is good enough for me.

TC Cooper mentioned that I should show the pistol re-assembled so the picture I took also includes the poor can that was the subject of the test.

Also I was curious to know what TC Cooper did after removing the seat using the dry wall screw trick. Was it replaced with a new seal? It would be interesting to know the end of the story.

For the time being, the problem was not the seat for the hammer valve as I first thought but it would certainly be useful to know all the possible options.

Thanks to all the people who replied to my post.

R-Gun Pete

R-Gun Pete

I've got a leak on my Alfa pressure vessel as well, and I found your posts very helpful - especially the exploded parts diagram. However, the dialogue box showing the part numbers and desciptions is a little blurry. I'm particularly interested in knowing the sizes of the o-rings.

Are you able to say where you got the original diagram from? Or could you provide a pdf copy?

Thanks in anticipation.

Mainliner