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Thread: Hatsan Model-125 with a stiff piston needs some luvin' attention

  1. #1
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    Default Hatsan Model-125 with a stiff piston needs some luvin' attention

    A friend was struggling to cock his Hatsan 125 and it was firing erratically. I was sure there was carnage in his chamber but when I opened up, spring whole, no broken bits, no chafe marks inside the cylinder. The only thing I can notice is a rock hard piston seal. So hard I had to hammer out the piston with more vigour than I enjoyed. But at last it is out and I don't think there is any lasting damage, it is a Hatsan after all.

    I'm very sorry to hear that MZE is no longer with us because I had just got to learn his name from his magnificent posts and I hope we will appreciate the wisdom of those posts for a long time still. My condolences to anyone who knew him personally and had the pleasure of meeting him in real life.

    I'm guessing that my friend left his black Hatsan in the midday Karoo sun and that cooked the piston seal rock hard.
    Pyramid Air says $11 ,
    "Fits Walther Falcon Hunter, Walther Talon Magnum and Hatsan 125 and Benjamin Trail NP XL

    For professional installation only."
    I'm no professional but I got the piston out without killing myself, I hope I will get it back together OK.
    Does anybody know who will post me a replacement seal for a good price?
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  2. #2
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    I forget now, is it a 25mm piston?
    Post a picture of the head of the piston.
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  3. #3
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    Jup I thought a photo would be worth a 1000 words but I was lazy ;-)




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  4. #4
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    Rashaad at outdoor pitstop has the seals
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  5. #5
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    Yes you will need an a new seal there.
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  6. #6
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    Quote Originally Posted by Kuberboef View Post
    Yes you will need an a new seal there.
    How can you see that? I thought the seal was OK except for being rock hard. There is a little bit of brass turning stuck in the top of the seal. I'm worried where that came from. I hope it was dirt in the chamber when the gun was built. The edges of the seal are not cracked or worn.
    Rashaad says R120 for a seal.
    Last edited by Fr3d; 22-05-18 at 16:01.
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  7. #7
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    I think your seal looks still good on the rim. But inspect it also nearing tge centre for cracks. A new seal is also hard haha
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  8. #8
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    Looking at the condition of the rest of that seal I am convinced there is small damage on that lip.
    What grease are you going to use?
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  9. #9
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    My seal looked just like yours when i took it out, i got my replacement from Rashaad and you can feel the difference
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  10. #10
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    I've got some silicon grease and pellgun oil from Pyramid Air. If even good seals are hard then I'm going to have to look more carefully for the problem. The gun was very hard to cock and sometimes hardly fired. The piston was so tight in the main tube I had to hammer it out.

    Don't want to put the whole thing together only to find nothing is fixed.
    Rashaad's picture says 30mm and mine measured about 29ish so that might be wear indication.
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  11. #11
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    Forget that silicone grease.
    Go get a tub or tube of good old wheel bearing grease, works a lot better.
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  12. #12
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    Quote Originally Posted by Kuberboef View Post
    Forget that silicone grease.
    Go get a tub or tube of good old wheel bearing grease, works a lot better.
    Yes I love that molybdenum disulfide bearing grease (moly) but the americans were going on about their black tar grease. Only a very thin smear and it works magic they say. I'm glad to hear my bearing grease is also good for pellet guns. No combusting I hope?

    The flippen crows have been driving me mad all day and I just can't get a clear line on one. They are just too clever for me.
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  13. #13
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    Remember less is more here, and yes it will diesel
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  14. #14
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    Quote Originally Posted by Fr3d View Post
    Yes I love that molybdenum disulfide bearing grease (moly) but the americans were going on about their black tar grease. Only a very thin smear and it works magic they say. I'm glad to hear my bearing grease is also good for pellet guns. No combusting I hope?

    The flippen crows have been driving me mad all day and I just can't get a clear line on one. They are just too clever for me.

    Ordinary moly wheel bearing grease works well , no need for expensive exotic greases.

    Yes Crows are CLEVER good luck with your quest.

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  15. #15
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    Quote Originally Posted by Juniper View Post
    Ordinary moly wheel bearing grease works well , no need for expensive exotic greases.
    +1. Castrol MS Grease works perfectly fine and a 500g tub will cost less than R100 and probably last you a lifetime. Use it sparingly though, as Kuber mentioned, less is more in this case. I have used Janman's method of applying MS Grease to the inside of the comp tube for a while and it works very well. I get very good consistency this way.

    Janman quoted below:

    "When lubing the comp tube use a match stick head size amount of grease and smear it inside the comp tube. All you want is a very thin coating evenly spread as deep as your finger can go. Then a light coating on the seal behind the sealing face. No grease in front of the sealing face. Work the piston up and down in the comp tube until you can feel the seal moving smoothly, then remove and wipe any grease which may have accumulated in front of the seal. There will be a little dieseling with MS grease but it should be gone in under 50 shots. This is how I do it, works for me and should be good for at least 10,000 shots."
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