Dianna 240 tune-up (help needed)

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  • Dianna 240 tune-up (help needed)

    Just purchased a Dianna 240 classic and am considering giving it a tune up. Despite scouring the internet for days I am unable to find anything on it other than a thread from an overseas forum from 2008 shortly after they were first manufactured. Unlike the one in this thread mine has a T-05 trigger, an un-chopped spring and 2 rear pins instead of only one. If anybody has pulled down one such as mine I would be most appreciative of a step by step on how to go about it. Failing this I have a couple of general questions as follows:

    Many of the threads I have been reading on overseas forums say to use “heavy tar” on the mainspring. What exactly is this and where do I find it or a suitable substitute down under?

    This air rifle is rated at 580 fps. How difficult would it be (for two blokes) to strip it down and re-assemble it without the use of a spring compressor?

  • #2
    Hi Hobo Hope this helps




    • #3
      Welcome to the forum - whereabouts are you?
      I've got an older model 24. I imagine it'd be similar.
      The spring isn't all that heavy - just use a sash clamp to compress the spring.

      As for grease - find some sticky moly grease.
      The last lot I bought was Castrol LMM. The heavy tar is simply used to dampen spring twang.

      To strip, remove action from stock and remove the barrel.
      I put the whole cylinder in a sash clamp to take up the spring tension. Drift out the two retaining pins. Remove the trigger unit. Pay attention to how the pins were located as they are a bit of a bugger to get back in.
      slowly release the clamp and the breech block will slide out of the cylinder.
      You now have access to the innards.
      Polish up the various parts and away you go.
      If you've got questions, take some pics along the way and we'll try to help.


      • #4
        From the Diana's I've helped tune, usually the spring guides are a good fit. Once apart try the guide in both ends. Fit the guide to the end that fits better.

        Polish the spring ends & the piston.

        They also benefit from a top hat to centralise the spring in the piston end.

        If you want me to make you one, send me a PM.

        If you would like a copy of my Airgun tuning services newsletter, also send me your email address.

        Have fun,

        Matt W


        • Guest's Avatar
          Hobo with a shotgun commented
          Editing a comment
          Thanks for the responses so far guys. As far as I can tell, the 240 actually replaced the model 24 and was very similar in its initial design, although they seem to have made some distinct improvements over the years. From what I can see with the stock removed, it appears they have also changed the metal spring guide to something made from a nylon or poly based material. I wonder if this was a performance based alteration or simply a cost cutting exercise. Looks like I will need to invest in a sash clamp or knock up a spring compressor before I can go any further. Will be sure to take some photos as I go and post the results if and when I get around to doing the tune. In the mean time if anybody wants to beat me to the punch or post any experience they have had with this particular model, by all means please do so.