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Air nozzle staying retracted after upgrade


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#1 threadkill

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Posted 09 October 2008 - 05:03 AM

On my M4A1, I just installed a Systema ported piston head, Systema M130 spring, and a Systema (NB) Type 1 cylinder (to match 407 promy barrel). All seemed to go in okay, and after a few tries at controlling the spring, was able to close the mechbox.

When test firing, bb speed was low, so I opened it up and noticed that the air nozzle was staying retracted after bb feed. It was locked in the in position and would not budge. I can confirm that I tested normal in/out operation after installing the tappet spring. I could push the nozzle in and it would spring back out.

I opened up the mechbox and rechecked the gear timing as best could (referenced mechbox vids) and buttoned it up again. Same thing happened; would fire normally but the air nozzle is not returning to the forward position.

The rate of fire and trigger response seems fine on both single shot and on auto (just a quick burst to check).

I did notice that under the sector gear is a spring-loaded lever that seems to want to orient the sector gear a little more clockwise than the video would denote. This seems to place the push-nob on top of the sector gear just in front of the back curved surface of the tappet plate.

I was careful to make sure the anti-reverse latch was in position. Seems this is the part most prone to misalignment, but I did make sure the tip went into the proper hole in the top of the mechbox.

Does this seem a gear timing issue? Anyone else encounter this problem during an upgrade? I can take pics of the internals just before reassembly if helpful.

Thanks!

#2 Supraracer

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Posted 09 October 2008 - 06:14 AM

 threadkill, on Oct 9 2008, 09:03 AM, said:

On my M4A1, I just installed a Systema ported piston head, Systema M130 spring, and a Systema (NB) Type 1 cylinder (to match 407 promy barrel). All seemed to go in okay, and after a few tries at controlling the spring, was able to close the mechbox.

When test firing, bb speed was low, so I opened it up and noticed that the air nozzle was staying retracted after bb feed. It was locked in the in position and would not budge. I can confirm that I tested normal in/out operation after installing the tappet spring. I could push the nozzle in and it would spring back out.

I opened up the mechbox and rechecked the gear timing as best could (referenced mechbox vids) and buttoned it up again. Same thing happened; would fire normally but the air nozzle is not returning to the forward position.

The rate of fire and trigger response seems fine on both single shot and on auto (just a quick burst to check).

I did notice that under the sector gear is a spring-loaded lever that seems to want to orient the sector gear a little more clockwise than the video would denote. This seems to place the push-nob on top of the sector gear just in front of the back curved surface of the tappet plate.

I was careful to make sure the anti-reverse latch was in position. Seems this is the part most prone to misalignment, but I did make sure the tip went into the proper hole in the top of the mechbox.

Does this seem a gear timing issue? Anyone else encounter this problem during an upgrade? I can take pics of the internals just before reassembly if helpful.

Thanks!

the nozzle is not in the tappet correctly? can you turn the nozzle with your fingers?

John

#3 threadkill

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Posted 09 October 2008 - 06:28 AM

 Supraracer, on Oct 9 2008, 10:14 AM, said:

the nozzle is not in the tappet correctly? can you turn the nozzle with your fingers?

John

Thanks John!

With the nozzle still in the in position (have not disassembled the mechbox again), there is maybe a total of 1/16" rotational play, if that. I was very careful to seat the nozzle into the tappet plate, but will check to see if they are intact when I take top mechbox cover off.

Edited to add:

I did try hooking up a battery with the mechbox and motor installer in the lower receiver. The air nozzle is moving forward during the fire cycle and then retracting. However, from watching a utube video on a mechbox simulation, the nozzle stays in the out position until the trigger is pulled and then retracts to feed a bb. I may just be confused on the sequence and getting compression loss from something else. Will be going back in shortly....

Edited by threadkill, 09 October 2008 - 07:18 AM.


#4 threadkill

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Posted 09 October 2008 - 10:13 AM

I was able to remove the top of the mechbox without disturbing the gears. Here's a pic shot from my phone; pardon the quality. Perhaps it is a timing or gear installation issue; notice that the position of the sector gear is such that the teeth are still engaged with the piston. I expect in a correct installation, it would look the same as when installed; that is, the tappet plate notch thingy at about one o'clock; no teeth engaged with the piston.

I'm also wondering if the type 1 cylinder is a problem, but so many have used type zero without a gear change, just would not make sense.

When I removed the top, the tappet plate did spring back to the out position, making me think that the reason it's staying in is due to being jammed against the top of the mechbox. I was careful to ensure it was fitting in the guide in the top half when the mechbox was closed.

Posted Image

#5 Supraracer

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Posted 09 October 2008 - 02:33 PM

 threadkill, on Oct 9 2008, 02:13 PM, said:

I was able to remove the top of the mechbox without disturbing the gears. Here's a pic shot from my phone; pardon the quality. Perhaps it is a timing or gear installation issue; notice that the position of the sector gear is such that the teeth are still engaged with the piston. I expect in a correct installation, it would look the same as when installed; that is, the tappet plate notch thingy at about one o'clock; no teeth engaged with the piston.

I'm also wondering if the type 1 cylinder is a problem, but so many have used type zero without a gear change, just would not make sense.

When I removed the top, the tappet plate did spring back to the out position, making me think that the reason it's staying in is due to being jammed against the top of the mechbox. I was careful to ensure it was fitting in the guide in the top half when the mechbox was closed.

Posted Image


The little nub on the sector gear is under the tappet. It's the brass nub on the gear that engages the piston you need to pull the tappet part that looks like a trigger back to catch the tappet nub. Your tappet must be bent allowing the nub to go under the tappet rather then pull it back when it cycles. Push the nozzle / tappet till the bottom of the tappet is behind the brass nub not over it. As the sector gear spins this nub pushes the tappet back.

John

Edited by Supraracer, 09 October 2008 - 02:43 PM.


#6 threadkill

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Posted 09 October 2008 - 02:56 PM

John,

Thanks for the reply. I left the tappet in this position to show what was happening after I fire; the gear still engaged. With the gear still engaged, won't move, and pressure released from removing the cover, the tappet spring pulled the tappet back out again; the reason it show as it does. This was not the condition before reassembly.

As mentioned, I was careful to make sure the tappet nob (for lack of a better term) was a around 1:00 during assembly, and the tappet arm trigger behind it. Without this lineup, it would not be possible to close the mechbox because the tappet arm would be too high. Also, the air nozzle would not be able to move; all these tests were done initially. before firing, I could manually push the air nozzle in and it sprung back with no friction at all.

Hoping for other responses, including the KWA guys. I understand about the warranty issues.....

#7 brooklyn468

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Posted 09 October 2008 - 04:53 PM

I know this may not be of much help, but maybe trying to completely taking apart your gearbox, cleaning it and putting it back together may solve the problem. That's what I usually do when I have a gearbox related problem.

Good luck!

#8 threadkill

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Posted 09 October 2008 - 05:06 PM

 brooklyn468, on Oct 9 2008, 08:53 PM, said:

I know this may not be of much help, but maybe trying to completely taking apart your gearbox, cleaning it and putting it back together may solve the problem. That's what I usually do when I have a gearbox related problem.

Good luck!

Hey dude,

It does help, and I have retried more times than I can remember over the past day. I even reinstalled the original cylinder in reverse so that the hole is closer to the front; wanted to see what the piston was doing. Reinstalled onto the lower receiver with motor and handle; and then hooked up the battery. It actually stopped at different places with each cycle (air nozzle remains locked in), but did not want to fire it in that condition too many times. Does point back to a timing issue.

I might next try the original spring to see if that makes a diff. I've learned a ton over the last few days though, which is very cool; will try a few more times. If no cigar, I'll box it up and send to an airsmith. I have a new M9 Tactical PTP to hold me over......

Cheers!

Edited by threadkill, 09 October 2008 - 05:07 PM.


#9 Stealthmaster14

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Posted 09 October 2008 - 05:31 PM

Is your tappet plate on the tappet plate "rails?" (similar to the piston rails, only for the tappet plate)

Edited by Stealthmaster14, 09 October 2008 - 05:32 PM.


#10 threadkill

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Posted 09 October 2008 - 06:16 PM

 Stealthmaster14, on Oct 9 2008, 09:31 PM, said:

Is your tappet plate on the tappet plate "rails?" (similar to the piston rails, only for the tappet plate)

I have tried to ensure that it is. Under the plate (gun on side as shown in pic, the groove is over the trigger assembly. When assembled, I tried several times to ensure that groove in the top of the mechbox is centered over the tappet plate so it stays in position. Does this sound right? I've also assumed that once the mechbox is assembled, being able to push the air nozzle in and have is return smoothly also indicates that it's centered in the rails. Sound right?

Got an image to confirm that I am thinking of the right thing?

Thanks for posting!

#11 Supraracer

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Posted 10 October 2008 - 04:06 AM

 threadkill, on Oct 9 2008, 10:16 PM, said:

I have tried to ensure that it is. Under the plate (gun on side as shown in pic, the groove is over the trigger assembly. When assembled, I tried several times to ensure that groove in the top of the mechbox is centered over the tappet plate so it stays in position. Does this sound right? I've also assumed that once the mechbox is assembled, being able to push the air nozzle in and have is return smoothly also indicates that it's centered in the rails. Sound right?

Got an image to confirm that I am thinking of the right thing?

Thanks for posting!


Just so you know it is normal for the sector gear to partially engage the piston after firing. The motor sometimes doesn't stop quick enough. (This will make it appear the nozzle is stuck back because the sector gear is holding it back) You should always fire in semi auto after F/A before opening the gear box. They do make MOSFET with braking to prevent this. The only thing that pushes the nozzle forward is the tappet and tappet spring. The sector gear pulls it back. So if you did everything else mentioned above you may have compression issues. I feel your Tappet is working as normal but something else is causing the bb to not have velocity. I would put the gear box back together and install the motor with the gear box out and fire to watch the tappet / nozzle move in and out. Also put your finger over the nozzle to feel the compression.

John

John

Edited by Supraracer, 10 October 2008 - 04:13 AM.


#12 threadkill

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Posted 10 October 2008 - 07:50 PM

Good post John, and I did try a few test fires with just the lower receiver and motor attached. You comments about the motor's stop cycle was good to read as this seemed to be the case; fit my observations about the tappet plate movement.

In the end, I was able to get back together and shooting well. Not at home so do not have my crony, but the gun is shooting harder than ever. I also gained the skills to strip an M4 down to an open mechbox, change a part, and then reassemble in under an hour, so time well spent.

Cheers for all the help, gang!




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