Cutoff lever preventing semi auto

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LazzurusMan

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So, I did some work to my Sig a while back, and it STILL isn't firing right. I've taken it all apart again to make sure everything is sorted and reshimmed the gears, and as I was checking the aoe I realised my cutoff lever is preventing my sector gear from turning far enough to let the piston move forward. I've short stroked the sector gear by two teeth, could this be the reason why? Do I need to take one off the other end, or one off the piston to fix this issue?

The picture below shows the point at which the lever stops the gears from moving and you can clearly see the sector gear is still engaged with the piston.

View attachment 83579

 
Sounds like your cutoff lever is worn or too tight.

 
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EDcase said:
Sounds like your cutoff lever is worn or too tight.
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It moves freely, and the gears can even push the lever out of the way if I don't hold it in place, the problem is when there something stopping the lever from moving (which I'm guessing there will be when I put the fire selector parts back on) the gears can't move enough to release the piston.

It's like I've managed to add precocking to the gun, but that wasn't my intention.

 
Initially I missed that you short stroked it.

Did you remove the teeth from the start of the sector rack?

You have to remove the teeth from the end of the rack. 

 
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EDcase said:
Initially I missed that you short stroked it.

Did you remove the teeth from the start of the sector rack?

You have to remove the teeth from the end of the rack. 
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I did remove them from the start of the sector gear. I could have sworn the guide I was using told me to do it that way.

 
Well if it did then it was wrong.  You have to get a new one and take the teeth off the end.

 
EDcase said:
Well if it did then it was wrong.  You have to get a new one and take the teeth off the end.
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Been watching videos from the Airsoft tech on YouTube, and he says taking them off the release side causes tapet plate issues, and so does everything else I've read online.

However, almost all of the forums posts I've found about it say to remove teeth from the piston aswell.

 
when you say stopping the gears from turning, are you meaning that it's cut off the power supply or that it's physically blocking the sector gear?

because those are 2 very different issues.

if it's cutting off the power supply then unless you have a combination of a strong motor and active braking, then the gears should roll past the release point on momentum.

even if you've taken teeth from the pickup side, the teeth on the release side will still be in their original configuration, so the fact you've short stroked it shouldn't be the issue here as if you hadn't those teeth would still be there. (although yes it is conventional to take from the release side)

 
Adolf Hamster said:
when you say stopping the gears from turning, are you meaning that it's cut off the power supply or that it's physically blocking the sector gear?

because those are 2 very different issues.

if it's cutting off the power supply then unless you have a combination of a strong motor and active braking, then the gears should roll past the release point on momentum.

even if you've taken teeth from the pickup side, the teeth on the release side will still be in their original configuration, so the fact you've short stroked it shouldn't be the issue here as if you hadn't those teeth would still be there. (although yes it is conventional to take from the release side)
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Yeah, I forgot how cut off levers work.

However, after putting the gearbox back together and putting the motor and grip onto it for a quick test, semi is very unreliable. I'll get a few single shots out of it, then it'll be burst, then single, then burst.

Would it be a worn cut off lever? Would my short stroking have done anything?

 
worn cutoff lever is always a possibility, likewise changing gears can have different cam profiles that may not provide enough lift. i have at times had to just try out different col's until i found one that lifted properly for a given box/gear combo.

typically though that leads to full auto operation, as the system doesn't trip off correctly.

are you using active brake? because that can be tricksy in situations like this.

your short stroking shouldn't have caused this, as with all the teeth remaining (ie if you hadn't short stroked) then the release point and cutoff point won't have changed.

 
Adolf Hamster said:
worn cutoff lever is always a possibility, likewise changing gears can have different cam profiles that may not provide enough lift. i have at times had to just try out different col's until i found one that lifted properly for a given box/gear combo.

typically though that leads to full auto operation, as the system doesn't trip off correctly.

are you using active brake? because that can be tricksy in situations like this.

your short stroking shouldn't have caused this, as with all the teeth remaining (ie if you hadn't short stroked) then the release point and cutoff point won't have changed.
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I think my fet has active breaking. I bought it years ago and can't quite remember if I got the gate nano ab or just the gate nano.

I'll grab a new col and see how it goes

 
Active brake on a build that isnt fast enough to need it can be troublesome.

That said its usually by stopping at that sweet spot where the col locks the trigger rather than the reverse as you seem to be getting.

 
Could it be my shimming? The sector gear could be too high? I could try adding a washer being the col to lift it up?

 
LazzurusMan said:
Could it be my shimming? The sector gear could be too high? I could try adding a washer being the col to lift it up?
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it could be, if there's not a good overlap then it'll accelerate wear, or in the extremes the cam won't engage the col at all.

generally i tend to try and keep the sector as low as possible when shimming for precisely this reason.

 
Adolf Hamster said:
it could be, if there's not a good overlap then it'll accelerate wear, or in the extremes the cam won't engage the col at all.

generally i tend to try and keep the sector as low as possible when shimming for precisely this reason.
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Only problem is my spur gear was rubbing on something until I added shims to that, and now the sector gear needs to be high to avoid the spur gear. I've got to open the gearbox again to try and sort the overspin issue, so I'll play around with the shims and see if I can get the sector gear lower before I spend even more money on this now frankly rediculously expensive gun.

 
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Problem solved.

I'd forgotten that at some point my trigger trolly had broken and I had to shave down a couple of bits to make it sit level. This meant that the trolly didn't sit right for the col to push it up enough to cut off properly. I just glued a thin piece of plastic to the trolly where the col should hit it, and problem solved.

 
LazzurusMan said:
Problem solved.

I'd forgotten that at some point my trigger trolly had broken and I had to shave down a couple of bits to make it sit level. This meant that the trolly didn't sit right for the col to push it up enough to cut off properly. I just glued a thin piece of plastic to the trolly where the col should hit it, and problem solved.
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always something random.....

maybe grab a new set of contacts for the long run? 

 
Adolf Hamster said:
always something random.....

maybe grab a new set of contacts for the long run? 
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Not a bad idea. Next time I need to get the GB open (I hope it's a while) I plan to finish my "hair" trigger mod too. There's still a little play before the trigger trolly starts to move, and the trigger pull is very long on this thing. Just gotta put something in the back half of the trigger to get rid of the play, then I'll probably just glue a piece of plastic between the trigger contacts to reduce the pull.

A new set of contacts would hopefully come with a stronger spring too for a snappier trigger.

 
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