More Airsporter help please

[Airsporter1st]

Thank you all for your helpful suggestions.
I have purchased a standard main spring from one of the well-known suppliers. The spring has the same number of coils and the wire thickness is the same as the old one so I'm guessing this is not the cause of the problem.
My concern centres on the fact some of the thread has been removed from the part that screws in to the cylinder. It seems to me if that had not been performed the piston would not travel far enough into the trigger block to latch the main sear? Are the pistons from the MK1 and mk2 the same dimensions?
I have tried putting the gun back together minus the spring, pushing the piston by hand does not engage the main sear also.
I have inspected the pivot points and the piston and do not see any appreciable wear with the contact points, at least not to my inexperienced eye.
When operating the cocking lever it travels to its fullest extent limited only by the stud that is screwed in to the cylinder.
I am including links to some pictures that might better illustrate my situation.

http://i513.photobucket.com/albums/t...psmnxx9kx7.jpg
http://i513.photobucket.com/albums/t...psd9o5ytwa.jpg
http://i513.photobucket.com/albums/t...pssqonuhuc.jpg

Once again thanks for any suggestions or solutions that might be forthcoming.
Regards
Phil

Something is wrong with that trigger in the photograph. The main sear should be sitting lower under the force of the trigger spring acting at the back end and the vertical sear bearing surface should be higher than and in front of the main sear. Don't have a photo of how it should be at the moment, but yours is definitely not right.

P.S. Found a pic of how it should look before cocking here
P.P.S. You have not secured your Photobucket, so all your photos are available to be viewed. You eed to set your album(s) to 'Private' if you don't one anyone else to browse through them.