Replace main seals in Original/Gecado/Diana Model 10

These pages show the process of stripping an Original Model 10 (aka Diana or Gecado in the USA) to replace the main compression seal.
This design is unique in having two identical opposed pistons which move in opposite directions, governed by a rack-and-pinion system to eliminate recoil. The dummy piston even has a piston seal washer but without any sealing lip.

The sequence of stripping (shown in following pages in pictures) is as follows:
1. Remove grip scales
2. Remove trigger guard (careful with small spring!)
3. Remove steel shroud (Careful with other pins!)
4. Remove trigger and spring
5. Remove cocking slide pin and slide.
6. Remove small pinion cover screws.
7. Remove pinion covers and pinions.
8. Remove lock screw from spring cap.
9. Loosen spring cap 1 turn.
10.In jig, remove spring cap, springs and dummy piston.
11.Remove main piston.
On a clean bench, remove the grip scales and have a receptical for small parts available, preferably a magnetic dish. If you can get hold of a cutaway diagram or parts diagram, so much the better. Try http://www.gunspares.co.uk/


Remove the trigger guard which is held by a screw at the front and a pin at the back, which can be pushed out with a suitable piece of rod.




Take care not to lose the fine coil spring at the rear of the guard.


Note the small square spigot on the small lever in the frame on which the spring is located.

lever off the steel shroud which allows access to the rest of the trigger mechanism.

The sear mechanism is located inside the handgrip frame. Take care that the other pins, which may be loose, cannot fall out and allow the mechanism to fall apart. A piece of sticky tape on each side will prevent the pins falling out during the rest of the dismantling.