Airsporter MK1 trigger doesn't catch

[TeeD]

Last afternoon, my Airsporter MK1 .22 called it a day. One moment it was a happy shooting relic, the other moment it refused to catch on the trigger.

After opening it up, I saw that the pin inside the piston all of a sudden seems too short. When pulling back the underlever, this piston pin should push against that hammer-like part in the trigger assembly and hook behind it, but it doesn't. It just doesn't push far enough to free it from the trigger. There's just one or two mm extra needed.

It's not the trigger itself that needs adjusting, I made sure to look at that. Even disassembled, so without spring, I can not push that piston pin in far enough manually. I can see there's a thread that goes into the nose cone, but it's stuck solid. Besides that it seems impossible to adjust, because if loosened, it will rotate itself until tight again or completely loose.

Doesn't seem to be any excessive wear on the metal parts and if it were, one would expect a period of on/off functioning before going definitely off.

Any ideas on this one?

[flatrajectory]

It sounds as if there is some wear in the cocking linkage somewhere. The most likely place to look is the rear end of the cocking slot in the piston and also the end of the cocking linkage where it pushes back the piston. Try a blob of weld on the end of the piston cocking slot, suitably polished and finished off ,of course.
Pete.

[Airsporter1st]

Last afternoon, my Airsporter MK1 .22 called it a day. One moment it was a happy shooting relic, the other moment it refused to catch on the trigger.

After opening it up, I saw that the pin inside the piston all of a sudden seems too short. When pulling back the underlever, this piston pin should push against that hammer-like part in the trigger assembly and hook behind it, but it doesn't. It just doesn't push far enough to free it from the trigger. There's just one or two mm extra needed.

It's not the trigger itself that needs adjusting, I made sure to look at that. Even disassembled, so without spring, I cant push that piston pin in far enough. I can see there's a thread that goes into the nose cone, but it's stuck solid. Besides that it seems impossible to adjust, because if loosened, it will rotate itself until tight again or completely loose.

Doesn't seem to be any excessive wear on the metal parts and if it were, one would expect a period of on/off functioning before going definately off.

Any ideas on this one?

Is the loading tap coming up fully? I seem to recall having a similar problem caused by the loading tap indexing plate coming loose.

This can also happen if the trigger spring is broken - resulting in the sear pivoting upwards at the front end and thereby preventing the piston rod from entering the trigger housing.

[TeeD]

Cheers!

The loading tap is coming up fully and the piston can be pushed as far back until it hits the trigger housing, so no play there. The trigger spring is okay and seem to be all the other parts.

It's just that pistonpin that seems to have shortened. There's a bit of play where the seal is on the nosecone, but I can't seem to tighten or even disassemble that. Even with the cone treated with penetrating oil and hold in a vice (hate that), it just starts to damage the tip by twisting. It's that solid.

But that shouldn't be the problem, because even if I push it completely back by hand, the pin doesn't push back far enough. Strange, isn't it?

[Airsporter1st]

Cheers!

The loading tap is coming up fully and the piston can be pushed as far back until it hits the trigger housing, so no play there.

It's just that pistonpin that seems to have shortened. There's a bit of play where the seal is on the nosecone, but I can't seem to tighten or even disassemble that. Even with the cone treated with penetrating oil and hold in a vice (hate that), it just starts to damage the tip by twisting. It's that solid.

But that shouldn't be the problem, because even if I push it completely back by hand, the pin doesn't push back far enough. Strange, isn't it?

Very!

I guess you have already had a good look at the x-section on Chamber's website. This should hlp you see what is wrong.

If the piston rod were to come loose, the overall length would increase, not shorten. It sounds like something has broken or come adrift in the trigger mechanism.

At least its a definite problem and not intermittent, so the cause is just waiting for you to find it!

[TeeD]

It's pretty definite indeed, so you would think the fault would present itself in a silver dish.

But it doesn't...

As you can see on the picture, the piston is almost hitting the triggerhousing when it starts to engage the little hammer-like thing.
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But with the limited travel remaining, it doesn't come further than this:
Uploaded with ImageShack.com

The play in the piston tip is nothing more than this:
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And the wear on the parts is next to noting:
Uploaded with ImageShack.com

[jjjjjj]

I take it you have undone the nut inside the piston, it sounds to me that the nut inside the piston is lose and that's why its not cocking.