Ak74 Upgrades

Zitch

Zitch

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Cybergun AK74Us -

So after stripping down and seeing that a few things in my gearbox need upgrading, I am debating either just replacing/upgrading the worn parts or aiming for an increased ROF. Current basket/upgrades;

Piston & Head

Spring & Guide

Inner Barrel

Bucking/Nub

Nozzle

Cut off lever

all Springs

Mosfet

Current gears and motor seem fine however I am contemplating fitting a 13:1 gear set, bearings and new motor. Has anyone done similar and recommend any other things to consider or parts? I currently have a basket on AK2M4 just waiting on pay day! 

 
is it really that badly worn that all of that stuff is gone?

because if it really is then it'll be cheaper and easier just to buy a whole new box as a drop-in.

 
Adolf Hamster said:
is it really that badly worn that all of that stuff is gone?

because if it really is then it'll be cheaper and easier just to buy a whole new box as a drop-in.
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No not everything is that worn, piston seal is poor and old so id like to upgrade that to have a metal rack, the cut off lever is worn and does need to be replaced, and id like to add a basic mosfet as with the worn cut off it is over cycling. the barrel and bucking are just upgrades id like to do rather than are absolutely necessary.

 
are you sure the cutoff is worn enough to be causing the overspin?

reason i say is cutoff levers can be a right pain to replace, one of those parts that really highlights the "compatible-ish" nature of airsoft.

the piston seal can be heath-robinsoned by stretching (or if your fancy replacing) just the piston o-ring (assuming the piston itself is in good nick), likewise ptfe tape (or doing it properly new o rings) on the cylinder head can sort that end. metal rack isn't guaranteed protection (and arguably a sacrificial plastic part can be good) but if the original is chewed up then might as well (you may need to glue the rack in yourself or it can get ripped out)

i presume the spring guide replacement is to a bearing type? that is a worthwhile move as it means you can lighten the piston by not having a bearing in that end.

spring i'd leave for now until you sort the airseal- could be perfectly good just the air loss is killing it.

bucking/nub certainly a good option, ml macaron+autobot is my go-to combo these days.

nozzle make sure to check the length, unfortunately not just the length can vary but also the internal diameter so if you're gonna change the head and nozzle try and get the same brand.

mosfet wise, plenty of options for cheap and cheerful but i tend to like putting something like the nanoasr in as the wiring is identical to the higher end gate mosfets so you can easily swap to something like a warfet later down the line.

 
Adolf Hamster said:
are you sure the cutoff is worn enough to be causing the overspin?

reason i say is cutoff levers can be a right pain to replace, one of those parts that really highlights the "compatible-ish" nature of airsoft.

the piston seal can be heath-robinsoned by stretching (or if your fancy replacing) just the piston o-ring (assuming the piston itself is in good nick), likewise ptfe tape (or doing it properly new o rings) on the cylinder head can sort that end. metal rack isn't guaranteed protection (and arguably a sacrificial plastic part can be good) but if the original is chewed up then might as well (you may need to glue the rack in yourself or it can get ripped out)

i presume the spring guide replacement is to a bearing type? that is a worthwhile move as it means you can lighten the piston by not having a bearing in that end.

spring i'd leave for now until you sort the airseal- could be perfectly good just the air loss is killing it.

bucking/nub certainly a good option, ml macaron+autobot is my go-to combo these days.

nozzle make sure to check the length, unfortunately not just the length can vary but also the internal diameter so if you're gonna change the head and nozzle try and get the same brand.

mosfet wise, plenty of options for cheap and cheerful but i tend to like putting something like the nanoasr in as the wiring is identical to the higher end gate mosfets so you can easily swap to something like a warfet later down the line.
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Cheers, yea I had put ptfe behind the piston seal which sorted the air seal and to be honest the seal was fairly good with the nozzle so I should probably leave that alone I just wanted to replace it so i'm not relying on the ptfe for a good seal.

Yea I am planning on fitting a ML macaron 60 and the spring guide is so that it is a bearing type. The spring i was going to replace as it seems very short and has a very rough cut job. 

The cut off is completely rounded so I am presuming it is causing the over cycle however the mosfet addition should also help with this.

I do need to buy a chrono as well and want to have it at the start before I begin changing anything.

 
fair enough, sounds like that guns had some butchering done to it in the past.

chrono is always a good move, it's the second best thing to being able to actually shoot it at proper range to see what your consistency is gonna be like.

 
Yea it’s definitely had some history but I do like it and it’s turning into a little first project for me.  I’m excited to see what I can do with it. Already learnt a lot from it so it will be good to see what I can get out of it. 

 
So having done some more research and studying I decided to go back into the box today before I jump the gun and order bits I don’t need. Went further and pulled the trigger assembly apart also. 
 

so I wouldn’t say the cut off is worn, I also replaced the seals on the piston and cylinder and air seal is now good except with the nozzle, measured it up and shall be replacing the nozzle. 
 

I was also a bit less sure that the previous shimming was as good as I thought and it seems like it was shimmed too tight as after I had shimmed it the gears seemed to be able to freely spin a lot easier than before and sounds good. 
 

As for the over cycling, it seems to have all but stopped. Not sure what or why but it is 100 times better than before. I think fitting a mosfet to the unit should solve that issue. 
 

apart from that it’s just the nozzle to replace and possibly the motor as there is very little resistance when I spin the pinion by hand. 
 

quick re-grease and test fire and it is so much sharper and the FPS has definitely shot up (waiting on chrono to test) but the difference is really noticeable. 

 
Zitch said:
So having done some more research and studying I decided to go back into the box today before I jump the gun and order bits I don’t need. Went further and pulled the trigger assembly apart also. 
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sensible move, no sense paying money to fix something that ain't broke.

Zitch said:
so I wouldn’t say the cut off is worn, I also replaced the seals on the piston and cylinder and air seal is now good except with the nozzle, measured it up and shall be replacing the nozzle. 
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generally the nozzle is the one thing that can't really be improved that easy without a part replacement, especially the ones that don't have o-rings as standard.

Zitch said:
I was also a bit less sure that the previous shimming was as good as I thought and it seems like it was shimmed too tight as after I had shimmed it the gears seemed to be able to freely spin a lot easier than before and sounds good. 
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worth pulling everything except the gears from the box when checking, you also need to remember to try it with the box tightened up as what might be perfect with the box held together can lock up tight when you bolt everything together.

Zitch said:
As for the over cycling, it seems to have all but stopped. Not sure what or why but it is 100 times better than before. I think fitting a mosfet to the unit should solve that issue. 
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sometimes these things happen, if i had a penny for every time i've taken a broken thing apart, found nothing whatsoever wrong with it, put it back together and it's worked again......

Zitch said:
apart from that it’s just the nozzle to replace and possibly the motor as there is very little resistance when I spin the pinion by hand. 
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yeah that's weak magnets for ya, if the rate of fire is good enough don't need to replace it on that alone though.

Zitch said:
quick re-grease and test fire and it is so much sharper and the FPS has definitely shot up (waiting on chrono to test) but the difference is really noticeable. 
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little tlc goes a long way, like i said worth checking the air seal first because otherwise you'll end up hauling a much stronger spring than the fps you're getting merits.

plus it'll go miles to helping accuracy, and by extension effective range- the way to tell is shot-shot consistency being much lower than before.

 
Adolf Hamster said:
sensible move, no sense paying money to fix something that ain't broke.

generally the nozzle is the one thing that can't really be improved that easy without a part replacement, especially the ones that don't have o-rings as standard.

worth pulling everything except the gears from the box when checking, you also need to remember to try it with the box tightened up as what might be perfect with the box held together can lock up tight when you bolt everything together.

sometimes these things happen, if i had a penny for every time i've taken a broken thing apart, found nothing whatsoever wrong with it, put it back together and it's worked again......

yeah that's weak magnets for ya, if the rate of fire is good enough don't need to replace it on that alone though.

little tlc goes a long way, like i said worth checking the air seal first because otherwise you'll end up hauling a much stronger spring than the fps you're getting merits.

plus it'll go miles to helping accuracy, and by extension effective range- the way to tell is shot-shot consistency being much lower than before.
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Cheers, yea the nozzle currently fitted seems pretty worn and doesn’t have any seals so I’m thinking to replace with a aluminium nozzle either single or double o ring. 
 

The ROF is ok for now, I think I’d rather put the budget into a nice mosfet and chrono for now. Maybe a few games down the line I will look at further upgrades to improve the rof, 13:1 gears etc, but for now I’m just aiming for good consistency and reliability. 

 
Mosfet with precocking would be worthwhile if you use a lot of semi, otherwise i'd say go basic (ie no active braking) as ab can cause bad trigger lockups on v3's.

 
Adolf Hamster said:
Mosfet with precocking would be worthwhile if you use a lot of semi, otherwise i'd say go basic (ie no active braking) as ab can cause bad trigger lockups on v3's.
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Thanks a lot for that advice as I was actually looking for one with active braking. Will just go basic. 

 
Cheers, I was thinking either a perun ab or a merf 3.2 originally. Or I may just go simple and put a gate nano in for now. 

 
So having had my chrono arrive today I decided to test it before replacing a few bits. 
 

First chrono was around 230-240 FPS, and seeing as the rif is shooting a lot better than when I first got it im guessing it must have been sub 150 to begin with. 
 

Anyway, having double checked shims, replaced nozzle, piston, bucking and nub a quick  re-lube, it is now consistent between 308-310 FPS. The air seal on the cylinder isn’t perfect and a bit of ptfe has been put in for now. But I think once I replace the cylinder head and possibly put a tight bore barrel in I could get it upto 330. However I’m happy where it is now and shall leave it be until I’ve used it a few times. 
 

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