Once it is cocked back, its supposed to stay cocked until you pull the trigger.. but mines wont stay cocked, when pull down the cocking lever it doesnt catch, how do i fix that?

hold in right hand, depress cocking release with thumb, pull back cocking slide (takes some effort) till it locks out, push in on the lower front of barrel to rotate loading port to the up position (this won't move unless the cocking slide is pulled back), load BB in the top hole that is exposed (or a pellet in the lower hole), push loading port back down flush with barrel, push cocking slide forward. Marksman is now loaded. push safety button in so it is engaged. When in an appropriate place to shoot a target, push safety button back with your right finger (safety is off) and squeeze trigger.

1. Make sure that there are two disks loaded in the launcher. They must be pressing against the pressure switch at the top of the chamber. 2. Use a screwdriver to push in the T-shaped switch that would normally be triggered when the priming lever is closed. When both switches are activated, the trigger should be unlocked, allowing you to fire and to release the priming lever.

This could be a factory safety that the hammer and trigger do not move while in the cocked position. The barrel may be locking down purposely. Look near the spring or in the path of the barrel where it folds back up and look for a release button. What do you see?

I thought mine stopped cocking, but it is actually the trigger that has cracked and is no longer disengaging the locking mechanism which frees the spring allowing it to force the dart out. It seems to be a bad design as the plastic used for the trigger is either too flimsy or too thin at that point. I haven't found replacement triggers yet.

You aren't supposed to leave the timer cocked for long periods, probably because it could wear out the timer spring (similar to the reason you aren't supposed to store the camera for long priods with the shutter cocked).

I thought that you set the timer by rotating the timer lever 90 degrees or more counter clockwise (when looking at the front of the camera). The further you rotate the timer, the longer it will run. Moving the timer lever exposes the start lever underneath the timer. Pulling the timer lever counter clockwise (it starts out pointed straight up) will start the timer, and putting the start lever back in it's original position will stop the timer.

Once the timer is stopped it is possible to take a picture by releasing the shutter normally, the timer can be restarted, or the timer can be reset for a longer time. After the timer is stopped it should be restarted and allowed to count down to zero before the camera is stored. I'm almost certain that the timer can only fire the camera if the shutter is already cocked, so it is safe to release the timer and let it run down any time that the camera is not cocked.
Good luck and do rate the solution if helped

Check the trigger guard screws. If the trigger guard has been loosened or removed, it can effect the proper position of the safety actuating lever (the lever in front of the trigger adjustment screw), preventing a full cocking stroke.

I suggest calling 1-800-879-8000 or going to the Hilti.com website and downloading a schematic for this tool. Let me know if you need more help

spring for trigger came off

If you need a repair manual contact me. I purchased one a year or so ago to make repairs on a couple I had and have since scanned it in to my computer so it can be emailed out. It's a big file. If you're interested let me know.

The problem is actually the mirror box controlling mechanism and not the shutter it self ,strictly speaking. What is happening is that the locking /unlocking of mirror, when it is cocked, is gummed up by perished rubber bushings and rubber shock dumpers ( life span of 15-20 years max ) .
You need to get to the left hand side of the mirror box ( easy to locate once you take the m. box out ) and clean out with isopropanol ( can use benzine but is unhealthy ). Relatively easy but make a note of where the wiring goes ( shutter and l. meter ). And then also take care with the mirror box -cocking mechanism at the bottom ( draw picture of position before dismantling ).