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Confusing Feeding Problem


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#1 KXR4

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Posted 14 March 2011 - 05:01 PM

Hey guys, I'm having a feeding issue with a friends KM4A1 running on an 11.1v 15c lipo. Using the stock KWA Hicap.

I did some searching and didn't find anything quite like my problem so excuse me if the answer already here somewhere.

My friends warranty ran out a few days ago, so he asked me to teach him how to break his gun down and remove the mechbox if needed to for reapirs, etc. Well needless to say it was pretty simple. I showed him how to remove the gearbox (we never opened it at this point, just removed it from the receiver), and then reassembled everything. Once we got it back together we went outside to shoot, and it would not feed more than one or two bb's every time you started shooting. Full auto was the same, not wanting to feed at all. Before we took it apart, it pretty well with an awesome ROF. Maybe one or two misfeeds every 50 rounds.

I have double and triple checked to make sure a part was not left out. The hop-up is nice and springy, and meshes nicely when the gun is assembled.

So I start inspecting the magwell/hop-up area and it appears the air nozzle isn't stopping all the way back after each cycle like it should be. This seems to be preventing it from feeding anything into the hop-up. Upon further inspection I noticed if you fire enough shots, every once in a while the nozzle is all the way back. If you insert a mag at this point, it will feed and fire one shot perfectly, then will not feed any more.

My first thought was a tappet plate malfunction. Maybe stretched or cracked, causing the sector gear not to pull the nozzle back properly. So I opened the gearbox and inspected the tappet plate, along with the other internals. Everything looks perfect. I replaced the tappet plate just for good measure and it still has the same problem.

So now I am stumped. I am thinking maybe the lipo is just overspinning the gears too much and too fast to effeciently load bb's (I noticed the motor overspins a lot, causing the piston to almost always be half cocked), but it doesnt seem to make sense considering the gun was feeding well before disassembly.

Any thoughts?

Edited by KXR4, 14 March 2011 - 05:01 PM.


#2 gcw360

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Posted 14 March 2011 - 07:10 PM

You are sure the tappet is attached to the nozzle.  I know...duh, but I had to ask. :gun:

#3 KXR4

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Posted 15 March 2011 - 07:06 AM

Yea the air nozzle is seated properly in the tappet plate. I can push the air nozzle back all the way by hand and the tappet plate pulls it back just like it should. I just can't see anything wrong with any of the parts.

Will all the hop up parts interchange with a standard Marui two piece hop up? I have a spare and they look identical. Thinking of swapping it into the gun with a spare barrel to see if it still has the same problem.

#4 jdmathew

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Posted 30 March 2011 - 09:21 PM

I am having this same problem with a brand new m4a1.  Seems like the timing is of with the gears.  Air nizzle and bolt always rest in different axial (forward and back) positions causing double feeds and misfires.  Let me know if you figure it out. Im still under warranty and have a help ticket pending.

#5 Abrazaderas

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Posted 31 March 2011 - 01:37 PM

i have a KM16BR 2GX, and i have an 8.4 as well as a 9.6. i too get frequent feeding problems that didn't seem to be the case when the gun was brand new. it'll fire about 75% of the time, with streaks of firing fine and not firing at all. switching from semi to auto sometimes causes it to feed for a moment and sometimes does not.

How do i observe my nozzle to see if it is operating properly? i mean, what is it supposed to do when i pull the trigger, supposing that i'm watching it with the barrel and top removed.

Can someone point me to a guide on how to remove and open my gear box?

does this model come with a sector gear clip, and if not, what kinds of sector gear clips can be installed?

the last poster pointed out that the timing may be off on the gears. what can be done to correct this?

#6 jdmathew

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Posted 31 March 2011 - 05:06 PM

View Postjdmathew, on 30 March 2011 - 09:21 PM, said:

I am having this same problem with a brand new m4a1.  Seems like the timing is of with the gears.  Air nizzle and bolt always rest in different axial (forward and back) positions causing double feeds and misfires.  Let me know if you figure it out. Im still under warranty and have a help ticket pending.


Right out of the box, I was having miss fires and double fires every other shot.  Today, the 3rd time shooting the KWA M4-A1,  I did a thorough test of all possible combinations of the following components on the KWA KM4-A1 (a total of 12 combinations):  
Batteries:
   Generic 11.1V 1500mAh
   Matrix 8.4V 1600mAh
Magazines:
   Stock KWA
   Generic "Holy Cow" High Caps from Evike.com
BBs:
   Airsoft Elite .25 Precision white
   Matrix .23g white
   Matrix .20g white

After about 500 rounds, I am glad to say that I did not have a single miss fire or double fire, no jams, nothing.  I think the seals/o-rings were just a little sticky from sitting for a while, and the break-in got them running smooth.   The gun shot 100% consistent and beautifully (I really like the realism of a NiMH and the speed of a Li-Po).   It was more than accurate enough to shoot a soccer ball 100% of the time at 60ft and I've got my red dot zeroed in. AWESOME!  I'll probably do some fine tuning of the hop up and barrel later (got an EDGI coming) for advanced accuracy, but as far as reliability I am very please now.

PS  KWA is as good as they get for customer service.  My help desk ticket was replied to within 12hours and all questions I had were addressed.  An RMA was offered but thankfully not needed.   Thanks KWA! I just wish you were in Indiana so I could stop by.

I'm such an airsoft newbie LOL ( but that'll change)

Edited by jdmathew, 31 March 2011 - 05:19 PM.


#7 jdmathew

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Posted 31 March 2011 - 05:18 PM

View PostAbrazaderas, on 31 March 2011 - 01:37 PM, said:

i have a KM16BR 2GX, and i have an 8.4 as well as a 9.6. i too get frequent feeding problems that didn't seem to be the case when the gun was brand new. it'll fire about 75% of the time, with streaks of firing fine and not firing at all. switching from semi to auto sometimes causes it to feed for a moment and sometimes does not.

How do i observe my nozzle to see if it is operating properly? i mean, what is it supposed to do when i pull the trigger, supposing that i'm watching it with the barrel and top removed.

Can someone point me to a guide on how to remove and open my gear box?

does this model come with a sector gear clip, and if not, what kinds of sector gear clips can be installed?

the last poster pointed out that the timing may be off on the gears. what can be done to correct this?


Turns out, my posted issue above was not gear timing at all! Simply the seals/orings were "too" new. The last 500rnds have been perfect.

Take the mag out, look in the underside of the mag chamber and note if the air nozzle is visible up in the BB feed tube.  Fire 3+ semi auto shots and re-note the air nozzle position.  My air nozzle was in different positions after every shot for the first 200 rounds thru the gun.  Now it's almost always entirely back.  Fully auto is different (to be expected says KWA). The air nozzle seems to be in any position after a full-auto fire-run.  This is why when you are done shooting you must dry fire your gun on semi about two times to reset the piston. You must also do this before opening the upper receiver. - Veronica(KWA Staff)

I have had no more problems switching between semi and full auto.

#8 -JOE-

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Posted 01 April 2011 - 04:39 AM

I noticed some over-spin when running my Flight max lipos because they are too powerful. Went to a Kong Power 15c airsoft lipo and no over-spin, but less RoF and trigger response. AB Mosfets are your friend.:thumbsup:

Edited by -JOE-, 01 April 2011 - 04:39 AM.


#9 Abrazaderas

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Posted 02 April 2011 - 10:40 AM

well, it's not break in, that much i know. on average, i fire about 600 rounds a day through it with target practice, and play at least once a week, going through thousands and thousands.

now, when i pull the trigger on semi, the nozzle always winds up in the back position.

i have my gun upside down right now, and i dropped a BB into the feed tube. firing the gun on semi or auto only makes the BB bounce up a little... it does not feed and fire.

now, perhaps this is because the mag pushes them up into there with more force then gravity provides. so i'm putting several BBs in the upside down guns feed tube, and pressing the stack of bbs gently.

i pulled the trigger, on semi, three times. a BB has fed into the hopup, i guess, since the stack went down by one BB. when i open it, no BB is in the hop but they all fell out of course when i took my finger off.

now, i'll put a BB right into the hopup, close the gun and fire it... BB fired.

so am i correct in assuming that the issue is probably hi-cap mags? i have the stock KWA hicap, and two aimtops. the aimtops don't seem to feed quite as well, which alone is a strong indicator that it is at fault.

can different BBs affect feeding?

now, i notice that i can very slightly wiggle the nozzle. is that bad?

well what the f*ck, i just dropped a BB into the well as before, gun upside down, and it fired. it didn't last time. the gun had been fired on semi several times beforehand, so what could have possibly had an effect? it's firing them fine now like this.

watching more closely, i see that the BB doesn't necessarily get chambered when i drop it in. poking it causes it to fall into the chamber, and it fires. if the BB does not go all the way in, it just bounces when the nozzle brushes it. mmmh.

maybe the hop unit is improperly placed because i put some medical tape on it so it'd fit snugly. removed the tape. a few misfeeds, maybe three or four, but an aimtop mag just shot off a whole mag on auto with no problem - using sh*tty crossman .2 BBs.




conclusion: f*cking ghosts.

#10 Spiggy

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Posted 03 April 2011 - 12:30 PM

what brand of bbs are you using?

#11 Heathrow

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Posted 03 August 2013 - 03:33 PM

I had the very exact problem. My Lipo battery was causing the issue by seemingly firing too hard causing "half shots". Switching back to a lesser powered nun chuck fixed this immediately. Also made it sound cleaner as it no longer had an extra "bounce sound"/"hammer rattle" for lack of better description.


#12 gcw360

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Posted 03 August 2013 - 04:44 PM

View PostHeathrow, on 03 August 2013 - 03:33 PM, said:

I had the very exact problem. My Lipo battery was causing the issue by seemingly firing too hard causing "half shots". Switching back to a lesser powered nun chuck fixed this immediately. Also made it sound cleaner as it no longer had an extra "bounce sound"/"hammer rattle" for lack of better description.
Super Necro Thread.....really, it's over 2 years old....

#13 niko_gpsy

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Posted 09 August 2013 - 10:17 AM

View Postgcw360, on 03 August 2013 - 04:44 PM, said:

Super Necro Thread.....really, it's over 2 years old....

Didn't we hold a funeral service for this thread last year?  Return of the living dead............................lol

#14 Chuck S

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Posted 09 August 2013 - 02:16 PM

... and every time you guys (or I!) reply to it it kicks up to "new content."  Just lock the puppy so no one can reply.  Heck to any over-1 year or 6-month thread.  I'd think the forum software could do that automatically if there are no moderators moderating.

-- Chuck

#15 gcw360

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Posted 09 August 2013 - 04:17 PM

View PostChuck S, on 09 August 2013 - 02:16 PM, said:

... and every time you guys (or I!) reply to it it kicks up to "new content."  Just lock the puppy so no one can reply.  Heck to any over-1 year or 6-month thread.  I'd think the forum software could do that automatically if there are no moderators moderating.

-- Chuck
I wish....Honestly, it's contributed to my whorish habit of attempting to answer so many threads!




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