Never get out of the boat
Been asked to do a bit of work on one.
Its only putting out 2.8ftlbs. The guy who has it reckons its the mainspring, but I've never had one of these apart. Not entirely sure that this is the problem. The breech washer is a bit knarley to say the least.
Anyone with some experience with one of these?
1st Battalion Humberside Cavalier Rescue Deserters on the cut
I should be making swarf!
It is most probably the compression washer that has disintegrated into dust, a common fault on these with the Giss system. They are not the easiest guns to work on and a spring compressor is highly recommended as there is a lot of pre-load on the three spring system. Make sure that you mark the position of the pinions so that they go back in exactly the same position so that the two piston timing is correct.
Neil
Current airguns:- Steyr LG110: Steyr LP10: Air Arms HFT500: Weihrauch97 fully customised.
Dodgy Diana User
http://www.airgunbbs.com/showthread....piston-systems
This thread may help, inc links to resources.
Dodgy Diana User
Registered User
I've been repairing these since the early 70s. As has been said the early type piston washers disintegrate and the breech washer can be squashed so as to be inefficient. They will come apart with not too much difficulty but the mainsprings are almost 50% compressed so be aware. Re assembly is critical there has to be a 0.30 mm gap between the cylinder end and the stepped face on the front disc inside the end cap. If you get this even the tiniest fraction wrong you will destroy the innards as soon as you fire it. If you want to have a go I can give you factory instructions and special assembly tool data; to make life easier.
Not for the faint hearted, but I was importer trained, so got first hand instruction, fortunately. Loss of power is rarely due to mainspring problems, even well collapsed ones will do better than the gun you're referring to.
PM me if you want info, instructions or help.
Registered User
Just like to add that the critical setting of end cap shims mentioned is easily verified after assembly.
In truth we always check before dismantling 'cos may have been set up incorrect previously.
When correctly set the rack & pinion teeth will have back lash with gun not cocked.
In this state the threaded trunnions can be turned with finger grip after initial slackening.
If the teeth are under load the shim state can be checked by turning the end cap in increments.
If unscrewing produces backlash the shim is too thick. If tightening does it the shim is too thin.
Handy if no accurate measuring device to hand.
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