Cyma Aks-74u build list help

[Titchiemagoo]

Hiya everyone and thankyou for reading. I'm hoping someone could help please.

I have got a (CM.045A) Aks-74u vfc clone so a v3 gearbox,  I was told it had low compression when I bought it so upon testing it shoots a little limp and even on a 11.1 it  feels like something is binding up on the inside.

So I thought I'd replace the internals while I'm on so I'm looking for a list of upgrade parts that people has used and know work.

I'm looking ideally for faster firing and more range on a 11.1 as this is gonna be my main gun instead of my ak47 which I'll probably sell to fund the upgrades.

Or will build up the upgrades over time as money is tight.

Also the main thing is which mosfet do I go for, which midrange brand/model is the best in this circumstance. 

Any help is welcome and very gratefully recieved.

 

[Colin Allen]

Perun V3 Hybrid
SHS 16:1 gears
SHS Delayer chip
Maple Leaf Macaron yellow plus red nub (from AK2M4) 
XT inner barrel
XT cylinder head
XT POM piston head
XT pink 14 tooth piston
A decent brushless motor or an SHS high torque if cash is in short supply.

 

[Adolf Hamster]

Perun V3 Hybrid
SHS 16:1 gears
SHS Delayer chip
Maple Leaf Macaron yellow plus red nub (from AK2M4) 
XT inner barrel
XT cylinder head
XT POM piston head
XT pink 14 tooth piston
A decent brushless motor or an SHS high torque if cash is in short supply.

For 11.1 thats probably a sound ratio.

I would say the non-maple leaf nubs can sometimes be a bit off-square, so i'd typically go for the maple leaf branded one.

If cash is shorter then an external mosfet like an ab++ or warfet could be substituted.

 

[Colin Allen]

For 11.1 thats probably a sound ratio.

I would say the non-maple leaf nubs can sometimes be a bit off-square, so i'd typically go for the maple leaf branded one.

If cash is shorter then an external mosfet like an ab++ or warfet could be substituted.

An AB++ would be a decent somewhat cheaper alternative.

 

[Skara]

If going 16:1 or 12:1 I would suggest to use helical gears.

The reason is that 16/12 spurs have a weird tooth profile that tends to wear bevel gears much faster than 18/13 ratio gears, while helicals have dedicated bevel/spur gears for those particular ratios.

My Cyma Ak runs on:

• BOB (box o' bits) 13:1 gearset, short stroked by 4 on release;
  
• FPS high speed delayer;
  
• FPS tappet plate, modified to set the timing;
  
• Solink 35k Advanced Brushless motor (unibearing, so no arl needed);
  
• Unmarked spring, probably a M100/M110 to stay below 1J;
  
• Perun V3 Hybrid + Clicker;
  
• Lonex gearbox shell + motor cage;
  
• FPS 8mm solid bushings;
  
• FPS piston body, metal rack;
  
• FPS POM piston head;
  
• FPS alu cylinder head (I generally prefer plastic cylinder heads, this is just for testing);
  
• FPS cylinder (3/4 hole);
  
• FPS 19.70 POM nozzle;
  
• Begadi Nebo hop unit;
  
• Maple Leaf Super Macaron 70°;
  
• Prometheus 247x6.05 barrel;
  

This setup gives me 24/25ish RPS on a 7,4v and just about 35/36 on 11.1, very snappy and somewhat "quiet".

p.s. my barrel is shorter than the stock, I have removed the typical aksu flash hider and adapter. Stock barrel length is roughly 290/300mm iirc.

Keep in mind that these lists are a rough guideline, the wonderful world of airsoft tolerances may result in your parts not fitting together like mine or someone else's did.

 

[Titchiemagoo]

An AB++ would be a decent somewhat cheaper alternative.

Are they the ones that just go in between the lipo and rif lipo plug but you can also hardwire in.

 

[Titchiemagoo]

Perun V3 Hybrid
SHS 16:1 gears
SHS Delayer chip
Maple Leaf Macaron yellow plus red nub (from AK2M4) 
XT inner barrel
XT cylinder head
XT POM piston head
XT pink 14 tooth piston
A decent brushless motor or an SHS high torque if cash is in short supply.

Hiya, thanks for the reply. What would be the difference between 13:1 to 16:1. Like how it would perform. 

What I'm working with.View attachment 151235

 

[Colin Allen]

Are they the ones that just go in between the lipo and rif lipo plug but you can also hardwire in.

It has to be hardwired, but that is quite easy as you do not need to open a V3 gearbox to do so.  However, it seems that you are going to open the gearbox anyway.

Hiya, thanks for the reply. What would be the difference between 13:1 to 16:1. Like how it would perform. 

What I'm working with.View attachment 151235

It would run faster on 13:1, giving you a higher rate of fire and a marginal improvement in trigger response.

However, if using it on an 11.1v with 13:1 gears, you might be heading for premature engagement (PME), where the piston cannot go forward fast enough and is engaged by the sector gear as it is moving forward.  That gets messy.

 

[Titchiemagoo]

It has to be hardwired, but that is quite easy as you do not need to open a V3 gearbox to do so.  However, it seems that you are going to open the gearbox anyway.

It would run faster on 13:1, giving you a higher rate of fire and a marginal improvement in trigger response.

However, if using it on an 11.1v with 13:1 gears, you might be heading for premature engagement (PME), where the piston cannot go forward fast enough and is engaged by the sector gear as it is moving forward.  That gets messy.

Thanks for replying, I can solder fairly well, I used to mess around with r/c cars and changing connectors on lipos or rifs if there tamiya connectors etc. So I'm confident with that I think. So you think 16:1 is the best bet. Just wanted to be sure, thankyou ever so much for your help your a ? 

 

[Colin Allen]

Let us know how you get on!

 

[Konsta]

I recently bought a new Cyma CM045 for around 70£. So far I've done some preventative work (reshimmed and relubed everything, checked seals etc). All I changed was add an R hop and mosfet. The gun is very quiet now (around 82 decibels) even though its shooting 1.65 joules (local European limit is 1.7) Suppressor really makes this gun shine. Stock motor and gears give just under 20 rounds per second which is enough for me. Effective range is around 65-70 metres with 0.32g bbs. The sight rail is just a diy from left over rail that's bolted onto the dust cover. Overall a great replica that's highly durable and upgradeable



PXL_20250805_145413873~2.mp4

 

[Titchiemagoo]

I recently bought a new Cyma CM045 for around 70£. So far I've done some preventative work (reshimmed and relubed everything, checked seals etc). All I changed was add an R hop and mosfet. The gun is very quiet now (around 82 decibels) even though its shooting 1.65 joules (local European limit is 1.7) Suppressor really makes this gun shine. Stock motor and gears give just under 20 rounds per second which is enough for me. Effective range is around 65-70 metres with 0.32g bbs. The sight rail is just a diy from left over rail that's bolted onto the dust cover. Overall a great replica that's highly durable and upgradeable


PXL_20250805_145413873~2.mp4

Thank you for the reply. I think my issue is the cylinder and piston but also worn gears. It's a learn as I go type of thing. I'm finished externally bar suppressor, but there is a smaller smokey wolf type tracer coming out so that'll probably fit a pbs. That'll come later though.

 

[Titchiemagoo]

Just to update kinda, I ended up getting a chrono, and it's running at around 280-300 fps so I don't think that's bad and around what I keep my pistols at. 

So I don't think I need to start opening the gearbox quite yet. 

So other than replacing the hop rubber and nub with a mosfet how else could I liven up the performance,  would changing the motor really change it that much.

Also another quirk I've found, it won't run on a 11.1, fires fine on 7.4 but won't fire at all on 11.1

 

[Skara]

would changing the motor really change it that much.

Yes, as long as it isn't some stupid "high speed" motor. By high speed I mean those 40k+ neodymium motors, they're overly expensive for what they are and very limiting in upgrade routes.

Also another quirk I've found, it won't run on a 11.1, fires fine on 7.4 but won't fire at all on 11.1

Usually it's the opposite, especially when a weak motor is trying to pull a somewhat stiff spring. Care to take a video of the issue?

 

[Colin Allen]

Just to update kinda, I ended up getting a chrono, and it's running at around 280-300 fps so I don't think that's bad and around what I keep my pistols at. 

So I don't think I need to start opening the gearbox quite yet. 

So other than replacing the hop rubber and nub with a mosfet how else could I liven up the performance,  would changing the motor really change it that much.

Also another quirk I've found, it won't run on a 11.1, fires fine on 7.4 but won't fire at all on 11.1

In the first post, you said it was cycling on an 11.1v; have you tried a different 11.1v battery?

If you want to make it a bit snappier without too much outlay, an SHS high torque motor would be an improvement over the stock one.  However, check what motor you have in there first!  If you can run to it, something like this would be even better: https://www.ak2m4.co.uk/internal-parts/motors-parts/solink-lite-brushless-motor-31k-short

 

[Titchiemagoo]

When I first got it, it was cycling on a 11.1v it's a recent issue. I don't have another one to test so I'm running it on 7.4 as I've got loads of them. I might get another 3s when I upgrade the gearbox.

 

[Colin Allen]

When I first got it, it was cycling on a 11.1v it's a recent issue. I don't have another one to test so I'm running it on 7.4 as I've got loads of them. I might get another 3s when I upgrade the gearbox.

I cannot think of a reason why it would not cycle on an 11.1v other than a battery/connector issue.  As Skara stated, a video of you trying to shoot it using an 11.1v would be useful.  What charger are you using?

 

[Titchiemagoo]

I don't get it either, the 11.1 works on all my other rifs just not the aks-74u. I have the charger in pic, had it a couple of years with no issues. Charges all my other lipos, only difference is my 11.1 is li-ion and not lipo like all my others. It can't be a connector as the 11.1 works in my other rifs and the 7.4 lipos work on the aks-74u.  If never had a issue like it. It makes no sense at all. Maybe it'll sort its self when I put a mosfet in or buy a slim 11.1 lipo.

View attachment 154505

 

[Konsta]

With 11.1 you should consiser adding a mosfet. A budget option would be HAL V3. Mine has run well but I decided to change gears to SHS 13:1 and change the motor can to SHS HT (strong magnets) and SHS pinion. The stock piston didn't like this and the teeth wore down quickly. Stock O ring didn't work well at sub 10°C (fps unstable between 380-410 fps). Changed to 23.8 mm and yields stable 425 fps at all temperatures. Now I have a full steel teeth piston. Also got a mini PBS-1 for the looks. View attachment 156524


PXL_20251024_121226179.mp4

 

[Konsta]

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