CA SR25... cycling full auto when it shouldn't...

[Grounded_Pilot]

Hi guys!

My new(ish) SR25 is playing up and I can't quite figure out why...
It is the Classic Army version that is supposed to be Semi ONLY... however I have had no luck!

I put a new motor in, and a new spring, and tried my very, very best not to move anything I didn't have to and made sure it all went back in the same place!

I'm not the best with gearboxes and the internet isn't really helping! Can someone give me an idea as to what might have gone wrong?

I can't be running an L129A1 on full auto... that's just wrong. :p

Cheers for your help in advance!

[LazyMcCrazy]

Re: CA SR25... cycling full auto when it shouldn't...

Make sure the little spring is still attached to the selector plate on the outside.
I also found out with my CA gearbox that the cut off lever screw tends to loosen, make sure its tight but the cut off lever still moves freely.

[Grounded_Pilot]

Re: CA SR25... cycling full auto when it shouldn't...

Hmmm. I don't think that is the issue... if you mean the outside of the gearbox, connected to the fire selector?

Here's some images (sorry for the poor quality) of my gearbox... hope someone spots a blatent issue!
SP_A0899.jpgSP_A0900.jpgSP_A0901.jpgSP_A0902.jpgSP_A0904.jpgSP_A0906.jpgSP_A0907.jpgSP_A0909.jpgSP_A0908.jpg This gear (last) is the one connected to the tappet plate, and this is on it's underside... a little notch on the central column?

Cheers.

[johnnyj]

Re: CA SR25... cycling full auto when it shouldn't...

test how your cutoff works

turn your sector gear while holding the trigger back and making sure the selector is set to semi the cut off should knock the trigger back after 1 full turn , if it does not the cutoff will be worn or even the trigger block

[Grounded_Pilot]

Re: CA SR25... cycling full auto when it shouldn't...

mmm, it doesn't lock after one turn!

There is only one fire setting, so I assume it's on Semi! hehehe

Well that sucks... now to work out which part is broken...

[johnnyj]

Re: CA SR25... cycling full auto when it shouldn't...

just a standard m4 selector plate you have fitted , the guns body will stop the selector moving to full auto. If there is a tech or shop nr you just ask if you can rob/borrow some of the spare cut-offs as they can ware out fast on some guns

[Coski]

Re: CA SR25... cycling full auto when it shouldn't...

Hey bud. Let me know if you need money for a new cut off lever....only fair that I pay for it.

[Grounded_Pilot]

Re: CA SR25... cycling full auto when it shouldn't...

Thanks for the offer, but I might look at any reinforced gearsets!

Any recommendations?

[cannon_fodder]

Re: CA SR25... cycling full auto when it shouldn't...

I cant tell from your pic 5 and 8 but have you checked the position of the switch block spring?

assemble the gear box with just the trigger ,switch and the 3rd gear . Pull the trigger then rotate the 3rd gear 1 revolution anti clockwise. The switch should be lifted by the cut-off lever and a small spring should pull it back to its off position. If the switch is not being lifted then the problem is with the gear/cut-off lever. If the switch is lifted but stays forward it may be a fault with the switch or return spring. I've had both causing this. A worn cut-off lever in a V2 causing auto only and a distorted switch in a M14 was to stiff to return on its own due to being melted caused by arcing

[Grounded_Pilot]

Re: CA SR25... cycling full auto when it shouldn't...

I appologise for the awful images! Sadly my only digital camera is a camera phone... with a mere 2MPix!

I'll give it a try and see what happens! However I have a suspicion that it won't lock.

Also, it crossed my mind that I have never actually had reason to work out how semi works?
When it catches the cut-off lever, does it kill the connection to the battery? Would make sence to do that rather than providing a force which could stress the motor!

Cheers for all the help guys... I think I'm nearly there!

[cannon_fodder]

Re: CA SR25... cycling full auto when it shouldn't...

Also, it crossed my mind that I have never actually had reason to work out how semi works?
When it catches the cut-off lever, does it kill the connection to the battery? Would make sence to do that rather than providing a force which could stress the motor!

The trigger has a sear that engages with and pushes on a notch on the bottom of the switch carrier pushing it forward to make a connection between the contacts completing the electrical circuit and spinning the motor. In full auto the switch carrier stays there until you release the trigger then it moves back to its start position ready to fire again.
In semi auto the cutoff level comes into play and engages in the switch carrier when you press the trigger. Once the selector gear makes one revolution the cam on the underside moves the cutoff lever lifting the switch carrier up and over the trigger sear. The trigger stays still but the switch carrier now released from the trigger sear is free to be pulled into the off position by its own spring.The electrical circuit is broken and the motor/gearbox stops. When you release the trigger the sear on top slides back under the switch carrier until it engages in its notch. This allows a new pull on the trigger to move the switch carrier forward again to start a new cycle

[Grounded_Pilot]

Re: CA SR25... cycling full auto when it shouldn't...

Right, this is being bumped up because after receiving my new SHS gears and SHS cut-off lever, it STILL refuses to fire semi. I am concerned that the actual contacts have gone, they look a tad worn where the cut-off lever connects to it, to flip it up...

I'm not sure anymore! It's all rather frustrating!!! (However I still don't want to surrender it to the very expensive local gunsmith!!)

[richardy]

Re: CA SR25... cycling full auto when it shouldn't...

replace the trigger set with a new one, they are prone to as much wear on the plastic as the cut off lever is to wear yet its some how more acceptable to replace the cut off lever but never the trigger block.

Since youve already replaced gears and cut off lever its now time to replace the trigger block, if its still an issue after that build up the hight of the cut off lever on the switch block end a little.

[Grounded_Pilot]

Re: CA SR25... cycling full auto when it shouldn't...

I was looking at the trigger block.
Are they easy to find? I can't say I've ever searched for one (Opens a new tab).

I'm getting very temped to just buy a cheap A&K gearbox and be done with it!