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Marathon 03-11-2013 12:51 PM

help with a sick sterling
 
I just bought a used sterling and it is having a few issues. I am hoping mcb can get me on the right path:
I have a modern stp sterling. I am using hpa at 800 psi feed via a palmers stab. When aired up it does not leak. When I pump the gun it opens the valve and vents down the barrel. The venting stops when I take pressure off the valve. I have added some washers to the valve spring. I can now cock the gun when it is not aired up. If i gently and slowly cock the gun the valve will stay closed, However if I pump the gun quickly (with more force) the valve will open and vent. This does not change when I adjust the stab.

A few questions:
The valve spring that came with the sterling is the same size as a phantom valve spring. Is that the right spring? Sterling need what kind of springs ? spyder springs?
Can a sterling normally be cocked when not aired up? I know most nelsons cannot be cocked when degassed.
I am going to remove the stab and feed hpa in at full pressure and see what effect this has. Any other ideas?
The adjustable hammer does not seem to adjust. As I turn the inner screw nothing seems to move to increase tension on the main spring. I am I confused as to how the adjustable hammer is supposed to function? Can these hammers become uncoupled if turned too far?

That is about it for now. MCB I await your wisdom.:bowdown

turbowagonman 03-11-2013 01:15 PM

Quote:

Originally Posted by Marathon (Post 2650747)
I just bought a used sterling and it is having a few issues. I am hoping mcb can get me on the right path:
I have a modern stp sterling. I am using hpa at 800 psi feed via a palmers stab. When aired up it does not leak. When I pump the gun it opens the valve and vents down the barrel. The venting stops when I take pressure off the valve. I have added some washers to the valve spring. I can now cock the gun when it is not aired up. If i gently and slowly cock the gun the valve will stay closed, However if I pump the gun quickly (with more force) the valve will open and vent. This does not change when I adjust the stab.

A few questions:
1. The valve spring that came with the sterling is the same size as a phantom valve spring. Is that the right spring?

2. Sterling need what kind of springs ?
3. spyder springs?
4. Can a sterling normally be cocked when not aired up? I know most nelsons cannot be cocked when degassed.
I am going to remove the stab and feed hpa in at full pressure and see what effect this has. Any other ideas?
The adjustable hammer does not seem to adjust. As I turn the inner screw nothing seems to move to increase tension on the main spring.
5. I am I confused as to how the adjustable hammer is supposed to function?
6. Can these hammers become uncoupled if turned too far?

That is about it for now. MCB I await your wisdom.:bowdown

To answer the questions I can in order (I put Red numbers next to your questions)

1. I've never had a Phantom spring in my hands so I'm not sure on the specs
2. I can measure my Sterling springs that came with my gun in the 90's (I have some matched sets using my Chronograph to match the springs)
3. I cut down some Spyder Springs when I spring tuned my Sterling
4. I have a Proline Sterling and mine CAN NOT be cocked unless it's aired up, although I've heard of some being able to (AP Sterlings).
5. This I'm not sure on this since I have a "preadjustable" Sterling
6. I'm not sure on this one either because of my answer in the last question

I'll measure my springs when I get home from work and post the info on this thread.

James_Blond 03-11-2013 03:56 PM

sounds like you have a finely balanced valve spring, which may be a little weak(try stretching it a little, cut spyder spring can also work) or try some of the items below. With regulated hpa you should be able to run down in the 500-700 psi range. Just remember that too low of a pressure will cause chuffing during ATing.

your may need to screw your main pump rod(the big one, not the one going to the bolt) in a little bit further into the pump handle. Just make sure you know where it is before you move it in case you need to put it back where it was. If it is entering the gun to far, you might be cause the valve to open slightly when pumping fast.

the adjustable hammer screw moves within the hammer. If you adjust it too far one way it is possible for it to lose contact with the threading and free spin without going anywhere. Try adjusting it both ways a bit to see if it will move back and forth.

Tinman 03-11-2013 04:14 PM

Quote:

Originally Posted by Marathon (Post 2650747)
I just bought a used sterling and it is having a few issues. I am hoping mcb can get me on the right path:
I have a modern stp sterling. I am using hpa at 800 psi feed via a palmers stab. When aired up it does not leak. When I pump the gun it opens the valve and vents down the barrel. The venting stops when I take pressure off the valve. I have added some washers to the valve spring. I can now cock the gun when it is not aired up. If i gently and slowly cock the gun the valve will stay closed, However if I pump the gun quickly (with more force) the valve will open and vent. This does not change when I adjust the stab.

A few questions:
The valve spring that came with the sterling is the same size as a phantom valve spring. Is that the right spring? Sterling need what kind of springs ? spyder springs?
Can a sterling normally be cocked when not aired up? I know most nelsons cannot be cocked when degassed.
I am going to remove the stab and feed hpa in at full pressure and see what effect this has. Any other ideas?
The adjustable hammer does not seem to adjust. As I turn the inner screw nothing seems to move to increase tension on the main spring. I am I confused as to how the adjustable hammer is supposed to function? Can these hammers become uncoupled if turned too far?

That is about it for now. MCB I await your wisdom.:bowdown

I don't know what others call this particular problem but i call it Diving into your valve.. Theres a nut on the front of your marker where your pickup rod enters the marker. The nut acts as a adjustable spacer turn it in a outward motion untill your problem goes away. The nut is retained by your front frame screw loosen it first.

make sure to Remove the washers you added in the valve.

The adjustable hammer is for velocity.

Marathon 03-11-2013 05:04 PM

Lots of good advice in here. Thank you. I am going to work through some of this tonight. I will update accordingly.

turbowagonman 03-11-2013 07:02 PM

Well here is a picture of the spring measurements. I would look into maybe it being a problem like what James_Blond suggested

"your may need to screw your main pump rod(the big one, not the one going to the bolt) in a little bit further into the pump handle. Just make sure you know where it is before you move it in case you need to put it back where it was. If it is entering the gun to far, you might be cause the valve to open slightly when pumping fast."

http://i98.photobucket.com/albums/l2...pse98a677a.jpg

Marathon 03-12-2013 12:13 AM

Thanks for the help. I adjusted the bolt position. It now cocks without venting down the barrel. Now just to get the springs adjusted to get the velocity nice and consistant.

surein 03-12-2013 12:02 PM

Hey Jay - glad you got the leak fixed. STPs shouldn't cock without air - that's usually a sign of a heavy valve spring. You can cut spyder springs to size to help you with velocity control. I do have some, if you want.

oh also if you don't have enough air pressure going into your valve, it will leak as well.

Marathon 03-12-2013 04:58 PM

Thanks Surein. I am hoping to do some tuning tomorrow. I had 5 washers in the valve spring. That was causing it to cock when degassed. I am going to play around with different numbers of washes in the valve to see how that affects consistancy at the chrono. Between varied input pressure from the stab and various numbers of washers I should be able to find something that works.

surein 03-12-2013 05:08 PM

IMHO Leave the valve spring as is and muck around with the hammer spring.


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