Tuning Help! Can't fully fill Marauder

[ChrisS]

Some time back, my .25 Marauder suffered from the shattered poppet thing.....pow, fwoooosh. So I rebuilt the rifle. All new O-rings and of course the poppet. Now I cannot get back to 3000psi without having the thing lockup. I have to release all the air and re-pump it to 2500psi. It is still capable of full speed, as much as 900fps with a 20 grain pellet. What gives?!? I thought maybe the guage was in error but it seems to concure with both the other two guages on my compressor and scuba bottle...help!

Chris 

 

[Airgunmann]

Probably valve lock you would have to give it more hammer spring preload to get it to open the valve

 

[dizzums]

i dont know what the poppet thing is, but if you replaced something in the valve i would Imagine something is binding or too tight there .. be sure you got all the correct parts and in the proper order, theres gen1 and 2 parts floating around and they may be different or incompatible with each other ...

 

[Pruitt58]

Did you clean your poppet seat really well before you put the new poppet in?

 

[ChrisS]

Yeah, I did. Cleaned it all up really well. I found evidence of water residue in the air tube, so I went clear thru all of it with a good solvent. With the exception of the o-rings and poppet, all the parts are original, that's what I don't get...what changed? The poppet is black in color, are there different kinds out there? The broken one was also black, FWIW. I have the spring, hammer and valve port as tight/far back/open as they will go (max pwr), is it possible to make adjustments such that you cannot open the poppet at 3Kpsi? Do I need a new hammer spring?

Chris

 

[caesar]

Are you using the factory hammer? There are two adjustments for the hammer. Have those been adjusted? Specifically the 1/8” Allen.


I’m pretty familiar with Marauders but the valve is something I haven’t had to open other than to replace a spring.

 

[ChrisS]

Yeah, factory hammer. I have both of the hammer adjustments set for full pwr. One is the spring pre-load and the other is the stroke length. The valve port adjustment is just that, a screw that can be run in such that it blocks off the transfer port. Sort of a throttle adjustment. I have all three adjustment set for maximum pwr.

 

[Xbowsniper]

Chris,

You might want to back off on the hammer stroke length. Sometimes when higher power is desired, and hammer spring is increased, AND hammer length is increased. The hammer actually has less distance to the valve stem at rest, and there isn't enough distance between the hammer and valve stem to build enough momentum to open the valve. Keep your hammer spring where it is, and reduce the hammer stroke length. If this does not work, make sure that you adjust your transfer port to 3 turns from the bottom. Keep in mind of the grub screw when doing so.

Another possibility is that the valve spring is too strong. Most of the time. I have discovered that whether or not you want high power, or a lower power, a light valve spring is desirable over the stiff factory valve spring. The other factor as mentioned above, is a damaged/broken/bent valve stem preventing the valve from working properly. If you take the valve out, take it apart, remove the valve spring, and make sure the valve moves freely in the valve housing. If it binds, the shaft of the valve might be bent, or might be in need of polishing. You did say that there was evidence of moisture/water inside the gun. This is a very possible culprit. 

Tom Holland 

Field Target Tech 

Fieldtargettech.com 

 

[Airgunmann]

If your getting full speed at 2500 that means you're valve is opening up all the way when you put 3000 psi in more pressure on the poppet is applied if you have the hammer spring tightened all the way in and the hammer striker backed all the way back against the hammer it should open the valve unless the poppet size changed or the length of the poppet stem is longer also bottom out the valve screw all the way tight and back it out 4.5 turns take the top grub screw out first too if that doesn't work something isnt right but u said it was working at 2500 psi which would mean valve is opening and closing if it was bent it would stick at lower pressure to you would think 

 

[ChrisS]

Thanks guys, this all gives me some stuff to look into. I'm gonna tear the rifle down again and check a few things. Maybe replace that main spring.

Thanks all

Chris

 

[Airgunmann]

Take a look at everything may have to get a heavier hammer spring

 

[ChrisS]

So, before tearing the rifle down fully, I installed a new main spring. That did it, velocity back up to about 950fps with a 20 grain pellet and I can fire from a full fill of 3000psi. Thanks to all that chimed in on this.

Chris