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Theoben SLR98 gasram stripdown

Discussion in 'Technical' started by Andy, Jan 15, 2006.

  1. Andy

    Andy Administrative Staff Member Founder

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    Here it is :) http://www.airgunforum.co.uk/slrstrip.htm

    Theoben SLR98 Gas ram Removal
    **************************************************************
    Information below shows how to remove the gas ram from the Theoben SLR98 air rifle.
    The strip was performed on a UK spec 12ft/lbs version that was out of warranty, if you attempt the strip below on a gun that is still under warranty you WILL void all warranty's that came with your rifle.
    All the information below has nothing to do with the Theoben Ltd Company; the strip was produced by an air rifle enthusiast and not a qualified gunsmith.
    BY FOLLOWING THE INSTRUCTIONS BELOW YOU DO SO AT YOUR OWN RISK. ?
    Some of the pictures below show the stock still attached to the gun and other parts that are not in order of the strip, these pictures were taken at a later time from the actual strip
    .
    **************************************************************

    Tools needed for the job
    1 x 3/32 Allen key
    1x 1/8 Allen key
    1x 5/32 or 4mm Allen key
    1 x internal circlip pliers
    1 x flat bottom object (Pin punch)
    1 x Theoben gas ram pump
    1 x Chronoscope



    Start by removing the stock from the action.
    Using the correct size allen keys remove the two front stock screws then the two screws in the trigger guard and remove the trigger guard.
    Once the stock is removed from the action the next part is to let the air pressure out of the ram, this is done by removing the screw and small o-ring under the screw at the rear of the action.


    [​IMG]



    This picture below shows the screw and small o-ring removed

    [​IMG]



    Once removed you should be able to see the valve pin, you then need a flat bottomed object (I use a pin punch) to tap lightly on the valve pin to release the air.

    Picture below shows the air release valve pin inside the rear of cylinder.

    [​IMG]



    Tap the punch on the valve pin so that the air is released a bit at a time, if you tap too hard the air will come out in one go and will probably make a very loud screech.
    This sounds a bit like one of those rape alarms women use and WILL make you jump, you have been warned.


    Once all the air is out of the ram you then need to remove the large 0-ring, you can do this by pushing down on the ram with your thumbs so that is goes further down into the cylinder.
    This will give you the space to get to the underside of the large 0-ring, at this point remove the 0-ring with the same tool you used to release the air from the valve by just putting it under the top inside edge (12 0 clock position) of the o-ring and gently prize it out.
    Don't put the tool all the way under the o-ring as there is a circlip underneath it, and you could bend the circlip if not careful.


    The next picture shows the large 0-ring removed exposing the large circlip, it also shows the ram up against the circlip but this should be further down the cylinder in your strip.(Picture was taken at a later stage)

    [​IMG]



    Now that the large 0-ring is removed and the ram is pushed down the cylinder you can remove the circlip using your circlip pliers.

    [​IMG]



    Now turn your attention to the cocking arm link underneath the gun, remove the circlip (pictured below) and push the pin out to separate the cocking link from the underlever.

    [​IMG]


    At the other end of the cocking link you will see a small screw, you need to remove this screw as this is what pushes the safety catch on when you would normally cock the gun.
    Remove the screw so that when you push the cocking link towards the rear of the gun it will slide under the safety catch.


    [​IMG]



    The next stage is remove the gas ram and piston sleeve, in order to do this you will need to lift the main sear at the rear of the gun as this will catch on the piston and stop it coming out when you push on the cocking lever.
    Lift the sear with your fingers so that it is held away from the cylinder as in the picture below.
    You may need to hold the sear still before lifting it by putting one of your fingers at the other side of the trigger unit, as the sear moves back and forth, so putting your finger at the other side stops it moving away as you try to lift the other end.


    [​IMG]



    While you hold up the sear push the cocking link arm towards the rear of the gun until you reach the opening in the cylinder cocking slot.

    [​IMG]



    At this point the ram will be coming out from the rear of the cylinder.

    [​IMG]



    When you reach the opening in the cylinder with the cocking link arm you can remove the cocking link arm by turning it 90 degrees and lifting it out from the piston sleeve.
    When you have removed the cocking link arm you should be able to remove the piston and sleeve just by pulling the piston from the rear of the cylinder.
    You can also push on the piston sleeve at the same time with your fingers or any other tool that will fit in the cocking slot to help it piston assembly come out from the gun.
    By now you should have the ram and sleeve removed from the gun as in the picture below.


    [​IMG]

    Pulling the ram body from the sleeve will separate the two to give you access to the piston seal.

    [​IMG]



    Here's a front view of the piston seal.

    [​IMG]



    Here is another view of the ram and piston sleeve.

    [​IMG]


    When you have performed the work you intended on the ram, put your gun back together in the reverse order as above.
    Pressurise the ram using your Gas ram pump and shoot over a good chronoscope to ensure you have the rifle running at the correct power setting.
    Running your rifle over the recommended pressure will burn out the piston seal and your gun will become very harsh to shoot.


    Airgunforum.co.uk
     
    Last edited: Mar 13, 2018
  2. jaffaman

    jaffaman Well-Known Member

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    Location:
    wetson s mare ,somerset bs22
    gasram

    Hi there,I have just had a look at the strip down,very good,so can any one tell me how to strip down a hw90,,gasram.Are there, somewhere, some pics on this I can have look at,ie:- seal on the piston and seals in side of the ram itself,it would nice to know how it works.Thanks a lot and cheers,,,,,,,,,,,,,,,,,,,,Andy,,,,,,,,,,,,,,,jaffaman...:)
     
  3. Andy

    Andy Administrative Staff Member Founder

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    I will have a go at the HW90 next and take the ram apart once it's out of the gun. :)
    Most users damage the 90 just by removing the stock and not setting the trigger before putting the trigger guard back on.
     
  4. jonesy

    jonesy Newbie

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    Sorry Andy any idea when your go to do the HW90?
    Its just that my 90TB has lost power so thinking about a strip and tune Thanks
     
  5. Andy

    Andy Administrative Staff Member Founder

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    Allready stripped it just need to get the info and pics online now, will try and get it sorted this weekend.
     
  6. Andy

    Andy Administrative Staff Member Founder

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  7. Cove

    Cove Well-Known Member

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    Very handy stripdown Andy,much appreciated.
    Chris.
     
  8. dalle

    dalle Newbie

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    Hi.:)
    When I try to pump my Eliminator, the pressurised air just blows past the O-rings in the gas ram. The pressure does not even get to 0.5 Bar before it leaks out. I tried releasing som air out of it to get it smoother but this thing happens when i try to get it back to full power. It´s brand new and i can´t see a single fault on the o-rings. Any Tips of what is going on in my gas ram??
     
  9. Andy

    Andy Administrative Staff Member Founder

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    Are you sure it's the o-rings and not the schrader valve. ?
     
  10. dalle

    dalle Newbie

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    Yes, i tested with leakfinder. It´s not the valve. Not sure if it´s the outer O-rings on the brass part or the inner one sealing the black piston. Tried to remove the black rod from the stainless part with the allen key, in order so remove the brass but it is stuck. Not sure if some heat from a heatgun will loosen things up? The brass thing is really loose in the cylinder of the ram and I can´t understand how ever it could seal before i released the pressure?:(
     
  11. Stot

    Stot Post Whore

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    Anyone ever remove the barrel and or built in silencer from an SLR? Is it screw in? Loctited?

    I know the silencer is grub screw but removing these does nowt.

    Cheers
    Stot
     
  12. Andy

    Andy Administrative Staff Member Founder

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    Theoben do seem to like loctite, so it's probably that. :D
     
  13. Stot

    Stot Post Whore

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    So a bit of heat and a twist should get it then?

    Im thinking a shrouded barrel in there might be nice.

    Cheers
    Stot
     
  14. Andy

    Andy Administrative Staff Member Founder

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    Yes get the heat gun out, just tried mine and it's stuck solid when the grub screws are removed.
     
  15. Stot

    Stot Post Whore

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    Took a gander at the barrel this morning, there are 2 grub screws under the lever holding the barrel into the breach block too. Undid them and thats loc-tighted too... :D



    Cheers
    Stot
     
  16. Andy

    Andy Administrative Staff Member Founder

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    If you put a shroud on how will the under lever lock up. :confused:
     
  17. Stot

    Stot Post Whore

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    Well it depends how I do it. It will either be the same as it is now, using a figure 8 barrel band type of thing, or ill have a clip like an SMK underlever, only better.

    I'm starting off with a .22 MFR barrel and shroud so ill see what happens when It gets it here. but I'll be able to put it back to standard if I dont like it. :)

    Cheers
    Stot
     
  18. Stot

    Stot Post Whore

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    I Brought a BSA Goldstar yesterday. Nice gun but not as nice as the SLR.

    This has a push button catch on the underlever that would work well with my conversion i think. :)

    Cheers
    Stot
     
  19. Andy

    Andy Administrative Staff Member Founder

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    Just been looking on the Diana site, they have a MOD 470TH Target hunter underlever rifle, looks very nice indeed. :)

    [​IMG]
     
  20. Stot

    Stot Post Whore

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    Cant get the bloody thing out. Its press fit ill bet. Going to have to cut it and get it bored out. :rolleyes::(

    Cheers
    Stot
     

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