Tuning Weihrauch HW100 - strange spring

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Oct 2, 2015
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Hi all,

I don't know if there is someone with some expertise on Weihrauch HW100 (recent models) here, but I thought I'll give it a shout.

Had a HW100 years ago and thought to buy it again but this time for the keeps.

And so, there I was, happily tearing it apart to check if everything is ok, polish what had to be polish and all of a sudden there was a small spring in front of me

10mm in length by 4mm in diameter and 0.66mm wire thickness, quite a hard spring to compress.

I was working on a valve assembly at the time but can't find the place for it anywhere on/around the block

I've checked HW100 exploded view but there aren't any of a recent date and on the ones I've found there is no such spring



Does anyone have any idea of where does that little thing belongs to?



Any help would be greatly appreciated!



Thank you!

Regards,

Walt
 
"Tearing it apart to check if everything is ok"? What indicated there was a problem? I have an HW100, and this spring doesn't immediately sound familiar. But, I've never felt the need to tear apart and polish stuff, it's been great from the beginning. If it ain't broke....
Click to expand...

Problem indicators were:

- cylinder leaking air when screwed on the action, never had that problem with the old HW100 (faulty or old oring, I have new ones on delivery today so I'll check that out today)

- sharp edges where there should be none

- obviously used moderator (I really do not think that Weihrauch tests every moderator they produce or that they test the rifle with the moderator on), had a few of their moderators and all came clean

- some strange threaded and plugged holes on the action block that I've never seen on any HW100
 
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Your air leak is most likely the small O ring on the valve stem. These are known to need periodic replacement. Since the cylinder has to be removed to remove the barrel, the cylinder is taken off frequently by many owners, so I think spare O rings for that one is a good idea. The "strange threaded and plugged holes" sounds odd. Maybe you could post some pictures. Is this a new or used rifle? 
 
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The only two coil springs in the valve/regulator block are the poppet return spring and a small spring in the valve block assembly. That spring is not shown in the schematic because it is sold as a complete assembly. There is a spring, a ball and o ring inside. Go to the Huma website and look at the regulator installation instructions for the hw100 and you will see it.
 
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Brand new out of the box

Will get the pictures when I get home, I have a few

I've sent a message directly to Weihrauch but they are on holidays vacation until Monday
Click to expand...

Walt, I wish you the best in getting this sorted out, but I'm very surprised that you didn't take up these issues with the seller rather than tearing down a brand new rifle. I don't know if anything you have done prevents a warranty repair, which would otherwise seem appropriate. 
 
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sounds like the spring is for the Main Valve, and not the poppet, make sure the ball bearing is on the regulator side and the spring is on the air cylinder side of the main valve body. drop the ball bearing in first and the spring last.

IMG_0821.1641406820.jpg
 main Valve



IMG_0822.1641406821.jpg
main valve

IMG_0823.1641406821.jpg
Poppet
 
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Main Valve stem O-ring and main Valve seat O-ring can easily leak, it will leak out the weep hole on the bottom of the action block, test with soapy water or spit, make sure it is lubed well and the Main Valve is good and snug when tightened, not too tight maybe about 20-25 inch pounds, also the breech block O-ring can leak if damaged or if the barrel is pushing against the block to hard, I always install the breech block before installing the barrel so the breech block can fully seat in the block housing, as you can see in the picture of the Poppet and breech block O-ring, O-ring size is 12mm x 1mm

IMG_0823.1641407313.jpg


here's the Main valve stem O-ring and valve assembly

o-ring size is 3mm x 2mm

IMG_0821.1641407485.jpg

 
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Do not loosen or remove the Torx screws on the bottom of the Action block, those are plugs and bearing seals for the drill holes for the air ducts to the Breech Poppet valve, if you loosened them, you will need to leak test them, if they leak use high pressure sealant or Loctite 577 to reseal the treads. the center plug is an Allen grub screw, that has a sealing bearing in it and a seal ring, it is for a regulator test pressure gauge, it does not need sealant but needs to be tightened very snuggly, about 15-20 in/lbs or until it stops leaking.
 
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Walt, I have noticed a couple of times, a slow leak down in my HW100. Both times, the cylinder was not quite sufficiently tight. I snugged it down (not sure if I could even feel it move), and that was it. I'm very careful not to over tighten things, so occasionally I will err on the loose side.
Click to expand...

Yeah, I've done that before, if it's slightly loose, it will make contact with the bleed slot cut in the inside of the end of the cylinder and leak.
 
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Finally got around to this

Received new o-rings for the inlet valve and that solved the leaking problem

O-ring that was on the inlet valve was hard and dried out, have no idea how is that possible on a new rifle but it obviously is. That, plus the fact that inlet valve looks like it was submerged in water for a long time, all pitted and looks like it was punched with a center punch. But that is mostly cosmetic and doesn't hurt the performance

IMG_20220104_163124.1641543000.jpg


I believe that I've found a reason for all these holes:

IMG_20220104_162205.1641543139.jpg
IMG_20220104_162156.1641543192.jpg


Old ones had only 2 on the bottom and now there are 4, old ones had none on the front of the valve housing, now there are 6
Looking down inside valve housing (impossible to get a good picture) all these holes interconnect as a plenum. That is the only logical conclusion that I could come up to, unless Weihrauch response differently. 

The oddest looking one is on the front of the valve housing with no apparent use or reason to exist

IMG_20220104_162151.1641544094.jpg
 

Biggest question that I had, the mystery spring, I think that I've figured it out.
It's all set up now so I don't have a picture but I'll get it as soon and I get 12x1 o-rings to change that crucial one (led by the logic if one is completely dried out and failed on a new rifle, it would be prudent to change all important ones)

@KatoKevin454 I'll borrow one of your pictures to help me describe, hope you don't mind 

It seems the Weihrauch has changed the logic on valve return spring. Instead of one quite good one, they have opted for the two bad ones

valve_2.1641544966.jpg


Thin and weak one (looks and feels like a spring from a pencil just a bit bigger diameter). There used to be a normal valve return spring in that place (just like on the KatoKevin's picture) but this one is almost useless in its current configuration. Short and stronger one goes behind the valve and it's not ground flat but coil wire is just cut so it digs into the thin and hollow end of the valve.

If I don't return this thing back, I think I'll buy an aftermarket parts for this and in addition, there is a spring maker near by so I could play a bit with different springs

I'm not new to HW100's, I had them before and worked on them quite a lot and shot few different configurations from other shooters but these design changes got me puzzled.
 
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