I doubt there's any serious issue with the gun. I had a similar problem awhile ago. It went away when I pulled and reinstalled the guard. I think it didn't seat properly and the safety was partially engaged, blocking the sear from dropping down to the piston.
Nowadays I install the guard as follows;
- Pressurize the ram just enough to push the piston forward and out of the way. Maybe 1-2 strokes on the pump.
- Cock the trigger, using a screwdriver. It's at 9:15 on the youtube video that Chuck-in-Ohio linked to.
- Place the trigger guard assembly into position. Line it up using the screw holes. Now press the round safety button (not the safety reset lever). This will allow the assembly to drop past the safety. Then wiggle it some more to make sure it's seated. Lightly pull the trigger. You should hear a slight click and it will drop that last little bit.
- Look closely at the guard, is it seated all the way around? It can fool you.
- If unsure, pull the guard out and try again.
- Install the screws.
Here's the full instruction from the Beeman RX/HW90 manual. It covers both disassembly/reassembly at the same time. So it's kinda confusing. I'm not sure why it says to uncock the trigger because you won't be able to put the guard back on unless the trigger is cocked. (See youtube video above). But their tip about holding the safety button is definitely correct.
- Secure the rifle, upside down, by the barrel, in protected vice jaws.
- Remove the trigger guard; this can be accomplished after removing front and rear trigger guard screws H2036 and H8942.
- Apply Loc-Tite to the front trigger guard screw only when replacing.
- When replacing the trigger guard unit, ensure that the safety retaining pin is in position; it is supposed to protrude a little for easy removal.
- Next, make sure the trigger mechanism is not cocked. If it is, uncock it by pulling the trigger.
- Now — VERY IMPORTANT — hold the safety button in the OFF-fire position (red showing) while positioning the trigger guard into its cut out in the stock and also while installing and securing the front trigger guard screw. If the safety is not held in the OFF-fire position it will bind on the sear (H2048a), and when the front stock screw is tightened, both parts could be damaged and/or broken.
- After fully securing the trigger guard screws, ensure that the safety button moves freely prior to attempting to cock the gun. The safety is automatic and will only come to its full ON position once the gun is cocked. Only with the gun cocked can the safety be reset from OFF to ON using the safety reset lever (H2058).
- Remove the stock by removing two H8940 screws, ensuring that you do not misplace their flat and lock washers (H2081a and H9283). When reassembling these washers, the lock washer goes onto the screw first. These screws must be treated with Loc-Tite when replacing and must not interfere with the cocking lever when secured. If they do interfere, more flat washers are required or the screw should be shortened.
Here's another tip. It's easy to uncock a HW90. It's similar to other Weihrauchs. Break the barrel, then pull it almost all the way back. Until it engages and compresses the piston just
slightly. While holding the barrel, press the safety. Then press the trigger. That frees the piston. Now carefully ease the barrel back up to its straight position.
Good Luck!
. Sear will engage piston if I cock the barrel and push the safety forward ( trigger guard not installed) . But after decocking it will not reset the safety and sear won’t engage piston!
