.25 Synrod teardown and some questions on parts please

[Rivers3Plinker]

My brother's .25 cal Synrod has been leaking since he got it. We took it apart last Sunday and replaced the o-rings on the valve and gauge block. A couple of the o-rings big chunks missing from them from the gauge port hole  but I'm not entire positive those were cause by our dis assembly when we pushed them out the tube. Anyway we put new o-rings on it and it still leaked afterwards so today he tried teflon tape on the gauge threads and that seems to have fixed it.

I know we would have saved some time finding the leak before tearing it down but we discovered more things as a result and I taught him how the gun basically works as well as how simple it is to work on it.

Findings:

• All of the baffles in the shroud were damaged because he double loaded pellets at some point
• Valve retainer screws on the sides were loose
• Exhaust port alignment of the valve is significantly offset to the left almost to the point where the seal hangs over the port
• There's what appears to be a set screw protruding into the side of the exhaust port on the right side

Questions:

• How can we properly align the port? I tested each screw and all of them pull the valve to the side offsetting the port alignment the same way. It's as if the valve was improperly machined or the tube punched offset. Grinding down the screw heads did not seem like a wise idea and would also allow for further misalignment unless some method of keeping the valve positioned is added
• Is Crosman the best source for new baffles or someplace else?
• Can someone explain the set screw and it's purpose in the exhaust port? I suspect it's a tuning aid to reduce velocity and increase shot count

I was also impressed with how much larger the hammer spring was compared to a Disco. We want to find a way to put an SSG in it.

Thanks all!

[Airsnipe]

I would suspect that the only good (safe) way to fix the misalignment of the valve would be to get a new valve. Sounds like it was machined incorrectly.

You can get the baffles from a couple other places other than crosman but I have no experience with that so can't recommend anything in particular. If your going to order another valve from crosman, I would just order some more baffles as well.

The set screw in the transfer port is for tuning like you thought. Although most guys back it out just to the point where it's not restricting the port but that depends on the power you want to achieve. It can be useful for low power tunes from what I understand. There should actually be two set screws in that threaded channel. One restricts the port and the other holds the that one in place so it does't move on you over time.

[Rivers3Plinker]

Thanks - makes sense on the screws in the port. Does anyone know, does Crosman tune them before shipping or just twist those set screws into the valve a set distance during assembly?

Amazes me they could machine that valve so far off center. We're talking the thickness of the transfer port seal at least. The seal barely hangs over the port.
I wonder if the transfer port bushing, since it is flat and puts pressure on the seal and the flat bore face of the exhaust port would keep the valve better aligned once the breach was installed if I reduced the OD of the socket head screws just a bit. I'm talking taking off the knurling on the screws is all. That might not be enough though. I just don't like the idea of monkeying with the screws because of the forces involved.

 

[moorepower]

Call Crosman.

[Frank in Fairfield]

Call Crosman.

Absolutely but it sounds like this .25 is 2nd hand, huh?

If it is new, you voided the warranty by opening it up.

If it is not new I would send it to a professional tuner (Daves Airguns in Sacramento, CA) and he will make it right.
Dave's is an authorized Crosman repair shop.
If it is not perfect, it will not leave his shop.
When he repairs an air arm, he airs it up to 3000psi and hangs it on his wall for one week.
If it loses any air he starts over.
He rebuilt my Crosman 1720T.....$65.00

That was two years ago and it still doesn't leak.
Good luck

[FuzzyGrub]

You are correct in that there is not any adjustment to correct for the exhaust/transfer port alignment.  As you stated it is either the airtube or the valve.   Using the breech screw holes see which one is off from the centerline.   A valve is around $25 and airtube around $50 from crosman. 

I'd take a clear picture and call crosman customer service.  You could indicate that you had the breech off to change to left side cocking.   They might not even ask why. 

[Rivers3Plinker]

You are correct in that there is not any adjustment to correct for the exhaust/transfer port alignment.  As you stated it is either the airtube or the valve.   Using the breech screw holes see which one is off from the centerline.   A valve is around $25 and airtube around $50 from crosman. 

I'd take a clear picture and call crosman customer service.  You could indicate that you had the breech off to change to left side cocking.   They might not even ask why.

That's a thought. I might try that although the valve body isn't all that expensive assuming that is the issue.
It's not a second hand gun. Brother bought it new from Cabelas ( don't ask why ).
He damaged the baffles himself double loading it.

Not worried about warranty. The gun was working really well, it just leaked down and we found the damaged baffles which were his fault. We never chronny tested it but it was still impressive.
I ordered the baffles and some stuff from Crosman yesterday. He seems happy with it now that it doesn't leak but we will chronny it and see where that goes. I more suspect the valve machining than the tube unless somebody else has experience with this problem being the tube more often. Otherwise will try a new valve body if he's not happy with chronny numbers and see if we get better port alignment and subsequently higher FPS. It's very accurate and plenty powerful now though.

Thanks all for replies

[n2omike]

I bought a .22 Mrod that had been leaking air...  They replaced o-rings, etc...  even added EXTRA o-rings...  and still leaked...  until they finally replaced the cheap pressure gauge.   

[Rivers3Plinker]

You are correct in that there is not any adjustment to correct for the exhaust/transfer port alignment.  As you stated it is either the airtube or the valve.   Using the breech screw holes see which one is off from the centerline.   A valve is around $25 and airtube around $50 from crosman. 

I'd take a clear picture and call crosman customer service.  You could indicate that you had the breech off to change to left side cocking.   They might not even ask why.

OK I just re-read your post and now I know what to check to figure it out. Makes sense.
Thanks!

[oldpro]

 I see this all the time with the holes not lining up and its almost always the pressure tube. What I do is grind the hole over with my dremmel tool and then use icemaker line you buy at LOWES and cut a .520 long piece and replace the transfer tube and seals.

[HillGSA]

I see this all the time with the holes not lining up and its almost always the pressure tube. What I do is grind the hole over with my dremmel tool and then use icemaker line you buy at LOWES and cut a .520 long piece and replace the transfer tube and seals.

  Rivers3Plinker


Please tell me you are not going to do that  ^^





Once you get the reservoir tube assembled ( valve assembly, gauge port, fill adapter housing, gauge, -  inside the reservoir tube ), double check that the 3- screws in the valve body are tight, the gauge is tight, and the fill adapter housing is tight. Then carefully fill the reservoir to about 600 psi - while listening for any air leaks. You should see the holes in the valve body and reservoir tube line up together - better - as the internal pressure pushes against the valve assembly. The factory valve assembly's opening usually moves slightly past the opening in the reservoir tube ( to the rear or butt stock end ). This is the best the factory parts will line up.


Many Marauder rifles have been sold and work just fine this way. It may not be perfect, but it works.


The Marauder rifles are designed to work with ( and not leak during the shot cycle ), the factory style transfer port and transfer port gaskets ( o-rings ).






     

[Rivers3Plinker]

I've done the icemaker line trick with my 2289G pumpers after opening the exhaust and barrel port but it's a hassle to get it right. Make three to get one that's the right length. Lots of trial and error. I'm not scared of the idea it just seems a little "shadetree" with this gun to me. Don't get me wrong, I bet it works fine, but it just seems out of line with this more powerful and expensive gun.

HILLGSA - I know what you're saying. The misalignment is to the left side of the port. Pressurizing is going to move it back a bit but possibly align it if there is enough clearance between the screw heads and the holes in the tube. This would be particularly true if one of the screws is out of round.
I guess if the screw heads were reduced OD just a tiny a bit, that pressure would force them to the center back of the holes in the tube which might improve alignment of the exhaust port if they are slightly out of round or the holes slightly offset. That all depends on the center line difference FuzzyGrub mentioned.