STD-SLR stuck in Semi Auto mode

Hi all. It’s my first post here. Recently, I acquired a STD-SLR which I may say pretty good out of the box. However, natural instinct made me to to upgrades inside the gearbox as below:

1.3 spring
Metal gear
FightingBro 480 motor
13.5 tooth metal ladder piston/plunger
PEEK tappet plate
PEEK nozzle tips
Metal cut off lever
Metal trigger
Adequate shimming

Everything went well except for the semi auto function. Its just stuck and the gears turned very hesitatingly like not enough power from the battery. Full auto works a charm. The original nylon tappet plate snapped during the process but that perhaps caused by me.

The best thing is, my friend did a custom build SLR and have no problems at all with almost the same spec.

I have tried to trace all possible issues. Narrowed down to:
a) The metal bevel gear only have 4 notches, compared to nylon STD’s 6 or 8 notches. Could this be an issue?

b) I have tried to simulate the single mode cut off mechanism when i opened the gearbox housing. When turning the sector gears, the cut off lever does not really engaging smoothly. Could this be the trigger switch module too tight? This is i believe where the parts from STD company as opposed to custom SLR builds.

c) Shimming the gearbox (although the engraving says Jingji SLR) is PITA. No matter how hard i tried, the gears will have some kind of restrictions when i apply even a tiny pressure on the nylon shell by hand. Yes, its nylon but not really a sturdy one.

d) i used 4 different 11.1v batteries, no sign of any improvements.

e) adjusting motor height doesn’t do anything except for less noise.

I know, there is a thread for this:

But maybe we could find out the real culprits and solve this issue with a discussion here.

I’m suspecting the trigger switch box and bevel gear’s 4-notch design could be the cause.

Cause the semi-auto was perfect in stock gearbox setup.

Yes man finally someone else addressing this major annoying ass issue, so many people just live with it and say “meh who uses semi anyway” I’ve tried so many things and I haven’t even tried to upgrade anything else besides the oring and cylinder head

I’ve tried a lonex trigger assembly to try fix it but it made no difference for me

Tried metal SLR trigger no difference

The only way to keep semi is by never opening the gearbox

I’ve bought a new gearbox and haven’t touched anything besides the spring and semi works flawlessly

And then like you said some people can open them and have no problem at all, I hear of all these shops and places opening the SLR gearboxes and modding them with no semi problems I’m assuming

I’m really hoping for an easy fix for this semi problem

Yes, nothing beats the feeling of having fully functional blaster including the mode selector.

For my case, the issue here is only the STD-SLR version.

If opening the gearbox here seems to be the case, maybe there is something related to cut off lever mechanism affected by the additional stress and tension caused by those upgrades.

Can we relate this problem with v2 ■■■■■■■ gearbox too?

If so, the gearbox shell must be it. Because if flexes like crazy. But i don’t know if swapping to metal housing can resolve this issue.

i have an STD-SLR gearbox and i think it may have a V1 SLR gearbox as a V2 SLR t-piece wont fit inside the STD SLR receiver, i haven’t opened one of the V1 boxes up because i want semi to work lol, I’ve only opened V2 SLR gearboxes and all had the same semi issue, so if you’ve opened up an STD SLR gearbox then its safe to say the same issue is prominent on both versions, it must be some way the gearboxes are put together like as soon as you open it up SOMETHING just clicks out of place and semi magically stops working ughhh

The is a response on another thread about the cut off lever maybe being a bit tight

Might be worth checking.

I’ve seen it a couple times with The wells

Thank you @zeHamish for this input. I will try to loosen up the cut off lever. Maybe to do all possible measures one by one to narrow down the cause.

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just a little update here, loosing the cut off lever does affect how it works. Now, semi auto mode acts like full auto now. I am assuming there is a precision adjustment need to be done here before tightening back the cut off lever screw. A little bit off and semi auto will be full auto. A little bit far and there will be not enough contact for the switch.

The only thing is, the adjustment will involve disassembling and reassemble the gearbox, motor and grip until u get it right. Unless u got a transparent switch assembly to see how it is touching.

Having said that, how i missed Gen. 8 gearboxes now. Haha.

Finally, i could conclude this issue after series of disassembling and testing done these past weeks. For future reference, may I summarise as below:

  1. For those STD-SLR owners, this issue might happen to you guys sooner or later due to the quality of the trigger switch module. And also involves few other components that need to be also aware of.

The trolley part seem to be very easy to be worn off especially if u use metal cut off lever and metal trigger. Look at the picture to see (Part A), and it was only 2 weeks after I bought it. I did a minor repair on the latch and my STD-SLR semi auto works fine now. But, I’m waiting for a new switch module which I hope is made from stronger material.

The little spring which connects the selector plate and the cut off lever was also out of shape (i forgot to take the picture) so i changed it to a stronger one. The cut off lever must always be in this position when we set the selector to semi auto mode.

  1. When re -assembling this particular gearbox. It is best to fine tune and realign everything back. By understanding the mechanism of switching system, I emulated the switch cut off process manually by hand and once it work, just reassemble and the semi auto should be working again.

4.If your trigger always stuck at semi-auto, your cut off lever is not moving as it should and the trolley didn’t get through and no contacts was made. If you force to pull the trigger, part B will worn out and you will have another problem in the future, trigger will slips off and the trolley will be pushed back prematurely.

  1. Most importantly, do it by only attaching the hand grip and motor attached (not the whole receiver) so that you can narrow the causes down easily because it will involve a lot of tearing down and reassembling the gearbox.

Let’s consider this issue is solved. Cheers!


Just encounter the same problem with my slr cqb,

Hi I’m having the same problem with semi auto being stuck but auto is fine… What minor repair did you make…

I just replaced the whole set trigger switch module and problem solved

Thanks mate… Where about’s did you source the trigger switch module and what did you pay… It’s the module from the first picture with A&B marked on it?

Yes, that piece called gearbox trigger switch module/block. I got it from local retailer in my country. You can also find it online:
Alternatively, you can change the whole trigger module from mechanical to mosfets, but i am so inexperienced to even try that.

Simple advise, don’t mix metal and plastic/nylon parts when it comes to gearbox internals.

Thanks for the info… Must be the weakest link in the SLR-STD…

I agree, it may happen even if you never open the receiver casing and use single fire mode too often. Anyhow, not really a big matter, just a flaw in design or production. I am happy to share the diagnosis hence less headache to you guys. Cheers!