AK-74U Only fires in full auto
 

Alright, just to start, i'm completely stumped on this one.
My AK-74U just stopped firing in single fire, for some reason, and taking it apart, I simply can't see anything that's loose, or messed up threads, and all the contacts seem to be fine.
I've looked through everything in doc's corner, and didn't find anything quite like this.
Hope someone can enlighten me on this one.
It will only fire full auto, even in semi mode. Safe mode works. No teeth are grinded on the selector lever, nor is it loose or anything. Also, there's no gunk or anything. It's all clean.
It all seems perfectly fine.
I'll take pictures if it helps.

Thanks in advance guys

Might be the cut-off lever that is worn/bent or broken.
Or it might be simply stuck with some gunk/plastic/metal scrap.

Yup, check the cutoff lever.

Nah, it's pretty clean, smooth action too. Although if I push the little part on top that holds the spring, with a screwdriver, it moves towards the outside a little bit.
Is that what you mean by bent? Because there's no wear signs.
Also here pic
Attachment 38029

reinstall the sector gear. Now use a screw driver or your nail to slide the switch trolly forward. spin the sector gear and see if the cutoff lever engages and resets the trolly.

On safe, the sector gear does engage the lever, ever so slightly to make the lever come up, then resets. The trolly doesn't react at all to this.
Nothing happens on what i assume is semi and auto

put the selector plate onto semi. the cutoff lever should be resting flat like in your pic. if doing this test and the trolly doesn't snap back and resets, then the cutoff lever is worn.

I uh, wasn't too sure, but okay, you mean the trigger trolly right? It comes back just fine really, the lever gets into the regular position to let the trigger trolly go forward. It resets just right.
This is what youre talking about right? Screwdrivered in pic
Attachment 38030

In your last pic, the selector lever is not installed correctly. It's supposed to be under the trigger switch block. If you did not remove the trigger since last try, it might be the issue.

The trigger block should move a bit up/down. That is needed to be reset by the selector lever. The lever pushes the trigger block up to slip over the trigger lever, and jump back. When you release the trigger, it moves up again to let the trigger lever reset and drop down after.

Without any gear, if you install the trigger components (trigger, lever ans spring), you should be able to reset the trigger block by pushing/rotating the selector lever down, while holding the trigger pressed.

So wait, these tests shoulda been done with the trigger on?
I've done everything without it on there.

UPDATE (As of like, right now)
Reassembled gearbox, fixed motor on.
Fires in semi only in what's supposed to be safe mode.
Eveerything else on selector switch / rail / whatever is full auto.