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PTW troubleshooting


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Old September 12th, 2015, 17:36   #1
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Join Date: Feb 2007
Post PTW troubleshooting

#Work in progress#

Unfortunately, being extremely Japanese in design; these guns are NOT designed to function under semi-failure conditions like AEG's are, so at the sign of any issue you need to stop gaming and inspect the gun.

Also, as easy as ptw's are to work on, there are many subtleties and quirks you need to be aware of when you're working on them, as overlooking the smallest detail can sometimes cause catastrophic failures. If you're not familiar with the ptw system, you should probably have an experienced tech look at it.

A motor issue will almost always be marked by the red blinky light of death on the ECU.

#1: Easiest thing to check is the sector gear holes. You can rotate the sector gear by hand, just make sure those holes are clear.

#2: If your lower is open, and there's a lot of ambient light (like if you're outside on a sunny day), it will affect the operation of the IR detector on the ECU.
Note: If the receiver is split and your sector stops 2-3 teeth too far, very consistently, this is normal.

#3: Check your brushes! Most common issue. Remove the grip, look at how far the brushes have traveled towards the commutator. It's easy to pull them out as well, if the brushes are shorter than 4mm, chances are you just need to replace the brushes.

#4: Inspect the brush leads! 2nd most common problem I've run into; inexperienced techs accidentally soldering the brush wires directly onto the brush hoods. This often restricts the travel of the brush and holds it back from wearing into the commutator, simulating having short brushes. You just have to un-solder the lead from the hood.

#5: If all of the above is good, there's one surefire way to test if you blew a motor winding: Remove the grip and move the sector gear to it's normal start position, make a mark with a sharpie on the armature and housing so they line up. Then try to fire once in semi. Typically the gun will cycle but end up in the wrong spot (not like 3 teeth too far consistently, I mean like a completely random spot). Return back to the start position, and turn the armature one step, and repeat.
If you have a blown winding on the motor, there will be a "dead zone" in the rotation where the motor simply will not start up.

Low fps, air leaks, buffer tube shimming, regreasing, SS cylinder piston issue, and air nozzles.

In the event of any chopping, low fps, air leak, barrel side problem, or every 10,000 rounds or so, it's time to take apart the cylinder.
Broken BB chunks can sometimes travel back through the air nozzle into the cylinder and cause more problems, such as a slight pre-engagement of the sector gear.

Regreasing is as easy as it gets. Just pull the cylinder apart, clean it carefully, regrease with either systema cylinder grease or tamiya ceramic grease, reassemble and shoot a few times. Chronoing at an expected muzzle energy for you cylinder and barrel combo will indicate success.

In the event of a broken air nozzle, you'll cycle the gun but the air nozzle won't move. In very rare occasions, the nozzle will cycle, but have infrequent or frequent misfeeding.
Normally the nozzles break at the thin cross section on the radial holes, detaching the pickup ring from the air nozzle. Buy a new air nozzle B side, or a whole new air nozzle. The nozzles are often loctited in place, so you'll likely need to heat the nozzle to unthread it. It is mandatory to use blue or red loctite to assemble the new air nozzle, or future problems will be pretty much guaranteed.
I've had a nozzle break at the seating ring (the disc part where the B side nozzle rests on the cylinder head), which was causing an odd sound as the piston slammed forward. Not necessarily dangerous in itself, but the broken piece could have easily wrecked the cylinder wall.

In earlier ptw models, the CU-009 O-ring (that grabs and pulls on the air nozzle) was softer black viton. This O-ring would wear out quickly in just 5000-10,000 rounds. The newer O-rings are polyurethane and tend to last forever.

On some of the stainless cylinders, the aluminum insert was machined too large for the piston, and so there is notable vertical travel on the piston. This of course causes engagement issues between the rack and sector gear and can lead to further problems. The only "quick fix" to this issue is to use a velocity (FCC) piston body, which is slightly oversize.

Air leaks are most often caused by cylinders in need of regreasing, cylinder dents (nothing you can do about that), and poor buffer tube shimming.
Different brands of cylinders can require different buffer tube shimmings, as well as different brands of receivers.
To set the buffer tube shimming, you want to add shims behind the buffer tube cap until the receiver SNAPS together firmly. You don't want to see any *vertical* play between receivers once the cylinder is in, although side to side wobble can sometimes occur. When you cycle the gun and look down the magwell, you should not see the hop chamber or cylinder moving back and forth.

Magazines and Ammo
When your ptw chops or misfeeds, it's most often a BB or magazine problem.
Here's a basic list of what BBs tend to work in PTWs:
Keep in mind, every ptw is slightly different, as is everyone's idea of how a ptw should shoot.
Ex: Someone can think their ptw shoots great on KSC's, but I know BB bastards have better performance.
Also, even though Valkens, KSC's, and G&G BBs work in some ptws, does not by any means guarantee they will work in yours.
The staple goto BBs are green devils and BB bastards.

Mags should be taken apart and cleaned out every year. Although this seems very silly to AEG users, it can affect feeding in a ptw, it can help your accuracy if your BBs are picking up crap from your mags, and it will help your mags last longer. I personally have 2 systema mags that are almost 10 years old and still work great.
There are "heavyweight" and "standard" ptw mags, it simply denotes spring strength. FYI neither one of them are good enough to feed .30s.
Finding the right spring choice for your BB weight can sometime be a challenge. A large amount of ptw users only fill their mags to 50-70 rounds.
Using .25s you shouldn't have any issues, but with .28s you can run into issues, and at .30 or .32 you're guaranteed to run into feeding problems.
Most commonly, the mag will feed like crap, chop, and spit BBs for a while, then suddenly shoot amazing. This is usually because the spring tension is not high enough to move the weight of that many rounds fast enough. Easiest solution is to buy "MAG" brand mag springs, which are much higher tension than the stock springs.
However, too much tension will also cause chopping. A BB feeds up into the hop chamber, but there's too much pressure between that BB and the second BB, and the air nozzle doesn't have enough force to push past until the piston slams into the back of it. So some people run one MAG and one systema spring in the mag.
*Some people claim that too high of spring pressure causes the nozzle to angle off in the chamber, creating a poor seal with the hop chamber. This is not true, as the air nozzle literally has no room in which to angle off (There's about .003" of play between the air nozzle and chamber).
You can either increase the tension of the air nozzle spring, or swap mag springs again.
But typically, with the range and accuracy you should be getting from a hop-modded ptw, you really shouldn't need more than 50-70 rounds in a mag. Plus midcaps are for peasants.

Some brands of magazines don't work well with certain hop chambers, or even just certain PTWs. My honest opinion is to just use systema mags; yes they are crazy expensive, but like I said, I have 2 mags that are almost 10 years old and still work great and still work great in all my teammates PTWs.

Hop, Barrel, and cylinder porting
Not much to say on barrels, just get a good one. The systema EVO barrels are really good, as are ORGA and PDI barrels.
Stay away from crap like Vanaras, FCC, and Celsius. You spent $2000 on a gun, don't cheap out on upgrade parts and expect them to work well.
And clean it after every game. A barrel can start to lose accuracy due to fouling after as few as 100 rounds, so make your shots count and keep the barrel clean.
Barrel length, bore, and the physics behind the hopup are explained here
As far as market hops, the orga flat seems to be the only hop adjuster out there that provides consistent and really good results. There are some issues with the rubbers wearing out fast, but the issues seem to be few and far between.
The "hop mods" that myself and others do work on the same principle as hop mods on AEG's: more surface area = more backspin = use heavy rounds = more range and accuracy.

If you're getting a lot of hop variation; BBs fly up and down at random but still fairly straight, chances are the rubber sleeve is rolling around on the pin. Either glue the roller in place or have it replaced and glued.
Sudden loss of hop, or inaccuracy, usually means the rubber is torn.
If your hop seems like it's cranked up no matter how much you adjust it, the adjuster cage is likely broken and must be replaced.

The systema hop chamber is a solid design. There are no aftermarket hop chambers that "perform better", they only match performance.
The MDD/STTS/RWA chambers don't offer any better performance, only a more convenient adjuster wheel.
I've personally installed a few RWA chambers, they've all performed as well as the stock chamber with no air leaks or fitment issues.

A few people, including myself, have run into fitment issues between an air nozzle and a hop chamber. You may not notice during assembly, then during test firing you notice a lot of misfeeding, chopping, and/or large air leaks. It seems systema had a bad run of nozzles and a few of them are slightly oblong and will bind in the hop chamber.
I filed my air nozzle back into round to fix the issue, but you can just as well buy a new nozzle.

Unlike on AEG's, you only have TWO choices of cylinder porting on a ptw: full cylinder, or ported to a 14.5" 6.04 barrel.
As a rule of thumb:
Ported cylinder
6.01 - up to 16"
6.04 - up to 14.5" (at 16" you might get better joule creep on heavier ammo with a full cylinder, I don't really know)
6.10 - up to 10.5"
unported cylinder
6.10 - 14.5"
Anything longer than 14.5"/16", not that you should ever use anything longer than a 14.5" barrel in an airsoft gun anyway.

Never slap the buffer tube, and never slap the rail to split the receivers.
This is the safest method, as show on
Slow and steadily applied pressure is safe. Suddenly applied shock force is a good way to break nuts loose, but it's also a good way to break castings.
Flash hider on your foot, stock on your pelvis, grip facing away, put both palms on the upper and slowly press the receivers apart.
Slapping the stock or rail can sometimes result in the receiver swinging open to it's maximum range and snapping the front body pin lug off the upper. It can also in rare occasions results in the lower receiver snapping between the buffer tube threads and rear body pin hole, or the RIS thread breaking off of the front of the upper receiver.
The systema upper and lowers are machined complex castings, and so are subject to casting cooling faults and cracks. Most notably on the body pin lugs on the upper receiver.
Real upper receivers will fit with some minor modification, real lowers with a lot more complex modification.
SGT makes the most solid 7075 billet aftermarket receivers. They're RS grade.
Prime has the best "airsoft grade" aftermarket receivers, 6061, sometimes not much more expensive than a RS upper.
Stay away from G&P (the lowers have the motor hole machined in the wrong spot), and FCC (Where do I even start...).

Electronics and Batteries
Waterproofing. It works.
The primary infiltration area for water is the bolt catch. The treacherous dick basically forms a slip'n'slide right into the side of the ECU.
There are a number of waterproofing products you can use, I've found "neverwet" works VERY well. You only want to spray the ECU and selector boards. The mosfet has the potential to overheat if insulated by waterproofing, and if the mosfet gets wet it usually means your gun is under water anyway.
Some people simply use chapstik or dental wax to seal the receiver, I prefer waterproofing, but it doesn't hurt to do both.

Last edited by ThunderCactus; September 18th, 2015 at 17:35..
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Old January 7th, 2016, 22:42   #2
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Join Date: Jan 2008
Location: Victoria, British Columbia
Excellent trouble shooting post. I wish you had wrote this earlier haha. One question about the grease is does it have to be specifically Tamiya Ceramic grease, or will any Ceramic Grease Suffice?

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