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My KM4S-TAC Just Stopped Shooting! AGHHH!


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#1 apollolanding

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Posted 02 November 2008 - 08:36 AM

I was just out on the range and was firing semi and auto bursts when all of a sudden the gun stopped shooting.  No grinding, heating, noises, misfeeds, smoke, jams or blown fuse.  I opened the receiver and no FOD, obvious problems, nozzle is extended, tried several batteries...nothing!  Any ideas, solution suggestions?  I'm past my 45 day warranty period and have put around 25,000 rounds through it.  No internal mods except a Mad Bull Bucking.  Never abused or taken a fall.  14 days until my next game!  AGHHH!

#2 Doctor Kajita

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Posted 02 November 2008 - 10:44 AM

Check all your wire connections and the tamiya connectors as well.

#3 apollolanding

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Posted 02 November 2008 - 12:01 PM

View PostDoctor Kajita, on Nov 2 2008, 01:44 PM, said:

Check all your wire connections and the tamiya connectors as well.

I'm way past that point now.  I've got the motor out, mech box out and a voltage meter that shows 10V going into the mechbox and 0 volts coming out despite having the fire selector switch set in every position and the trigger pulled.

CRAP!  It's always my luck... I buy one of the best brand of "insert device of your choice here" and a month after the warranty expires, I'm the 1-1,000,000 that gets the dud.  Mp3 players, LCD TVs, computers and now airsoft... I'm cursed...

#4 vic_man4

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Posted 02 November 2008 - 01:28 PM

View Postapollolanding, on Nov 2 2008, 01:01 PM, said:

I'm way past that point now.  I've got the motor out, mech box out and a voltage meter that shows 10V going into the mechbox and 0 volts coming out despite having the fire selector switch set in every position and the trigger pulled.

CRAP!  It's always my luck... I buy one of the best brand of "insert device of your choice here" and a month after the warranty expires, I'm the 1-1,000,000 that gets the dud.  Mp3 players, LCD TVs, computers and now airsoft... I'm cursed...

Could have burned out your engine, I dont know what happens when it burns out (heat or noise) cause it has never happened to me, but see if you hook your battery directly up to your motor and if it works, then thats one thing to cross off the list of posibbilities.

#5 triple b

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Posted 02 November 2008 - 02:35 PM

sound like u burned out the trigger switch....volts going in none coming out...

#6 vic_man4

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Posted 02 November 2008 - 05:09 PM

View Posttriple b, on Nov 2 2008, 02:35 PM, said:

sound like u burned out the trigger switch....volts going in none coming out...

I never even thought of that o.o :lol: KWA apparently has the best trigger switch.

#7 brooklyn468

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Posted 02 November 2008 - 07:17 PM

Well you may want to decide on something fast, because if you need a replacement you may want to order it before your war.

I found out the hard way, I didn't have a battery do I bought one too late and I borrowed my buddies for the war. It was a Sanyo 600 mah NiCD. Great fun!

#8 Doctor Kajita

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Posted 02 November 2008 - 08:49 PM

View Posttriple b, on Nov 2 2008, 02:35 PM, said:

sound like u burned out the trigger switch....volts going in none coming out...

Yeah, that was going to be my next guess.  Get a mosfet.

#9 apollolanding

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Posted 06 November 2008 - 10:34 AM

I've isolated it to the trigger or selector switch.  Tonight I'll be cracking open the gearbox to see which one.  The only other thing I can think of is that a wire inside of the mechbox came loose/unsoldered.  I'm hoping that's the case as my father used to be an electronics instructor at a nuclear power plant training facility and taught me NASA Spec soldering.  While I'm in there I'm going to replace the OEM wiring with 14 or 12 gauge (if it fits through the receiver into the RAS) wiring.  If the trigger switch/selector switch is bad it looks like I'll be ordering a 3rd party switch/wiring assembly as I don't see an OEM one in the KWA pro shop.  I've got 8 days to get this thing back into shape or else I'll be begging for a loaner or *gasp* renting a gun...

#10 triple b

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Posted 06 November 2008 - 12:30 PM

crack it open....i was scared at first but it not that bad.....i watched mechbox.com like 5 times till i had the process down in my head step by step......then i took it apart.....go slow... I mean slow, organize all the screws where they go ( take a before picture for reference) and go slow ....( i took 3 hours with breaks to take apart and put together) oh yeah get ur replacment parts first too, u dont want to take it apart and put it back together the next day on your first time....trust me it never works the process is not fresh in your head.

#11 triple b

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Posted 06 November 2008 - 12:33 PM

just a suggestion....just replace the broke parts first to make sure you have fixed the problem....you dont want to fix multiple things at once because u may find u put it back together and it doesnt work... then ull be looking a wiring problems and the trigger switch or selector switch.....

#12 Guest_allizard_*

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Posted 06 November 2008 - 12:39 PM

You can always call us directly and we can find you a set of wires.

#13 threadkill

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Posted 06 November 2008 - 12:46 PM

I recently installed a mosfet so have dealt with the wiring. A few considerations:

Heavier gauge wiring might fit through the opening in the mechbox, and might squeeze past the gears and down to the motor, but if too thick, you will not be able to reattach the wireguard that sits on the left side of the mechbox. If it sticks out at all, it won't clear the lower receiver. This should be your very first test fit. If too stiff, it will not snake around the front of the air nozzle and fit under the plastic wedge that sits in front of the feeder tube.

On my M4A1, the existing solder connections on the trigger switch looked perfect; would seriously doubt that you have a cold or disconnected solder joint.

There are already a few instances of the trigger switch on these guns going out. Although it may not be on the KMA sight, you should email support and ask the question. They have been very responsive and helpful to all of my inquires.

#14 apollolanding

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Posted 08 November 2008 - 04:38 AM

I sent KWAUSA an email describing the problem and to their credit they said that if I shipped the gun to them they would fix it for a flat fee (it was an extremely reasonable labor fee) plus parts.  I didn't have time to ship it and get it back in time for my game so I took it to a local airsmith guru in New Jersey.  Hey opened the mechbox and discovered it wasn't a wiring or switch problem at all.  The little piece of metal that is cast into the gearbox that holds the trigger switch in place had sheared off.  He said that it was a problem even with the highest end gearboxes (he's fixed 2 KWAs and at least 4 Systema boxes with this problem).  He looks at me and says, "so you think you're looking at a new gear box case right?"  I dip my head and my debit card starts leaping in my wallet.  He smiles that veteran gun/airsmith smile and says, "I'll take care of you."  He commences to drill out the area where the trigger post was, inserts a small screw with Locktite, Dremmels off the head and threads and voila... better than new."  He then marvels at all of the upgrades KWA has made to its guns since he last worked on one.  I ask him if there is anything else I should replace preventative maintenance wise and he holds up the piston and says, "this oh wait, nevermind, they've changed the first tooth.  This is much better."  He checks compression and was amazed at the tight seal the piston head created in the cylinder.  Then he checks shimming and declares that while he is going to add a .5mm shim to one gear, it was nearly perfectly shimmed at the factory.  Everything else in that 50,000 rounds fired gearbox was in great shape!  As he reassembles the gun he's amazed at how smooth everything went together (I had it disasembled for him when I brought it in).  He said, "this is like a metal Mauri with improvements!"  That made all of the anxiety I felt about my broken gun fade away.  This guy knows guns, nearly every serious airsoft player in the state of NJ knows who he is, has purchased a gun from him or had him fix a gun.  He loves Mauri and constantly praises them on various message boards and in his shop. So to hear him say it was an improved Mauri made me realize the time I spent researching which gun would be my first HPEG, the money I've invested in the gun and the trip to have it repaired were all worth it.

I was the unlucky one.  Do not hesitate to buy a KWA because of one little piece in a system of hundreds fails.  "Shite happens" to even the best gun, car, bike, guitar or any other high end "toy".  The great part is that even what seemed a costly repair ended up being 1.5 hours of labor, a screw, 1 shim, re shrinkwrapping all of the wires and a good cleaning.  She's shooting 380 with .25s and I'm a happy camper.  That number will margainally increase when I add my Systema 455mm tight bore and Blackside supressor (to hide the extra length).  I want to keep the gun at just under 400 fps with .25s so it doesn't get "tagged" for semi-auto use only on some fields.

So case closed.  Gun fully operational.  No loaner/rental needed for my match next weekend and no huge hole in my bank account.

Joe




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