ICS tappet plate issue?

[DanBow]

G'day chaps and chapettes, 

I've hit another problem with my AK74M. 

I've fitted the new piston set and compression is much better but now the BBs won't feed. At all! Set was piston, head, cylinder and nozzle from @ak2m4

After the bazillionth time of stripping and checking everything is sat properly in the gearbox, including that the gears were shimmed properly, I saw that the new nozzle is 19.7mm where as the old one is 18.8mm. So I put the old one back in but they still won't feed. Tried a full midcap mag and a fully wound high cap.

So, after lots of head scratching and Googling there seems be an issue with ICS tappet plates.  It's not snapped, which seems to be the main issue but do they become worn or can the start to bend over time?

I'll strip it again when I get in from work tonight but thought I'd ask the hive mind for their opinion.

 

[Skara]

Is the gun ICS oem or you just happen to have a ICS plate? Judging by the length of the stock nozzle I guess it's the former.

Are you using a delayer chip of any kind?

Tappet plates do wear out with time, the front of the fin (the only part that touches the sector gear, at least in theory) gets hammered with each cycle and some manufacturers insist on making these out of cheese (ICS is one of them), so it could be worn out to the point it doesn't fully retract anymore which in turn prevents it from feeding. All of this happens more quickly with higher ROF guns.

Get some pictures so we all can have a better understanding of what's going on.

 

[DanBow]

I bought it off here as an ICS so I presume it's all oem. 

Are you using a delayer chip of any kind?

Had to Google that! Lol No, not got one of those, just a standard gear.

Here is a slow motion video of down the feed tube.


20250224_220824.mp4



To me, it looks like it's just not retracting enough?

 What you said about the fin getting worn makes sense as it is an old, well used rifle. 

 

[ButcherBill]

Looks very inconsistant to me, has the tappet plate spring been stretched during dissassembly?

 

[DanBow]

Looks very inconsistant to me, has the tappet plate spring been stretched during dissassembly?

Don't think so. It still needs a good pull to attach it to the frame.

 

[ButcherBill]

Then is the nozzle tight on the cylider head?

the nozzle looks very inconsistant where it stops after a cycle.

 

[Skara]

That nozzle bouncing back and forth doesn't look normal, but it could be me.

If you turn the gun upside down and place a bb on the feed tube (without pushing it down) and fire a shot, does it drop in the right position?

 

[DanBow]

Then is the nozzle tight on the cylider head?

No.

If you turn the gun upside down and place a bb on the feed tube (without pushing it down) and fire a shot, does it drop in the right position?

 Tried that and no it doesn't  It bounces out.

 

[ButcherBill]

Does the sector plate have a flex to it? Is it possibly slipping off the sector gear pin before a full rotation?

 

[Skara]

 Tried that and no it doesn't  It bounces out.

That indicates that either the nozzle is too long or the hop rubber lips are. Is the hop rubber stock?

Does the sector plate have a flex to it? Is it possibly slipping off the sector gear pin before a full rotation?

Borderline impossible, there is a guide on the right side of the gearbox the plate runs onto, it keeps the plate from bending and doing what you described.

In any case the plate would have to bend so much it would snap in half regardless.

 

[DanBow]

That indicates that either the nozzle is too long or the hop rubber lips are. Is the hop rubber stock

With the new aluminium nozzle, it was noticeably too big but the one in the video is the original. Hop rubber is a maple Leaf but doesn't seem to protrude off the barrel any more than the stock one. I'll swap it out for the original later and try again.

 

[The_Lord_Poncho]

With the new aluminium nozzle, it was noticeably too big but the one in the video is the original. Hop rubber is a maple Leaf but doesn't seem to protrude off the barrel any more than the stock one. I'll swap it out for the original later and try again.

I'm betting that this will resolve it. I have a few guns that simply won't feed with maple leaf's, although the MR bucking lips are more forgiving that the longer macaron lips. Whilst Maple leaf are my go-to choice, I have also used G&G Green buckings which provide adequate performance and seem (mostly) universally compatible. 

 

[DanBow]

Sorry for delayed update.  . . . 

Put the original nozzle back in and changed the cylinder for the original too. The new cy6muat be fractionally bigger as the case now closes easier and the top strip slides on without the use of a hammer! 

It also shoots but only with the supplied hi-cap steel mag. Also, if I try to quickly single shot it, it dry fires every 3 or so shots but if I put it in auto it's fires fine! ?‍

I bought a few mags at the same time, from different sellers, but none seem to work right. Looks like I'm going down the try every mag manufacturer until.i find what works again! I ended up with 16 m4 mags beforei found the metal Nuprol ones were best!

 

[The_Lord_Poncho]

Have you tried swapping the hop rubber back to the original with no luck?

 

[DanBow]

Have you tried swapping the hop rubber back to the original with no luck?

Yes, the original is back on it.