Two round burst

Eien · June 6th, 2012, 16:50

I'm not the greatest with gearboxes so hope someone can help me.

I decided to reshim my gearbox but after I put everything back together. It started to fire in two round burst in semi time to time. Now it shoots fine but maybe like every 20 shots or more, it fires in two round burst. I was thinking if there was problems with the switch assembly but maybe it's my shim job?

I'm using a 9.6 NiMH battery.

tunabreath · June 6th, 2012, 17:19

If your sector gear is shimmed too low (to the left), it can interfere with the semi-auto cutoff lever. Larger diameter (not thickness) shims on the bottom of the sector gear can also interfere with the cutoff lever.

audi_bhoy · June 6th, 2012, 18:07

tunabreath got it right !!

L473ncy · June 6th, 2012, 23:44

I've heard of cutoff levers getting worn down on King Arms M4's.... Could that be it? Basically it gets worn down and doesn't always cut off properly.

If sector gear shimming is correct try replacing with a known good cut off lever and if it works flawlessly after a stress test then that's your problem.

Eien · June 8th, 2012, 03:13

Maybe I shimmed the sector gear too low.. not sure yet but I will check tomorrow. IIRC, it didn't had the burst in semi issue before I re shimmed it.

AngelusNex · June 8th, 2012, 18:52

If it's got a weak spring this can happen. friend of mine had this "problem" with his AK, was just cause it was a brand new powerful battery, after a few games it went back to normal as the battery broke in. Though if you have anything above a M90 spring I can't see this happening.

Spike · June 8th, 2012, 19:09

I have a 110 spring in my CA and it did the same thing... I switched to a lower voltage battery and it stopped.

Eien · June 9th, 2012, 15:03

I have a M90 spring installed in it but I was only using a 9.6v NiMH battery...

karl_azytzeen · June 24th, 2012, 15:19

This is an overspin issue.
The inertia due to the soft spring /high power motor makes the gears continue moving, despite the motor is not reciving energy (cut of lever works well)
This can be solved:
1) using lighter gears, like systema energy done in carbon.
2) stiffer spring
3) less battery voltage
4) (what I choose an the best with springs < 110) Mosfet with active braking.

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June 6th, 2012, 16:50	#1
Eien Trader rating Join Date: Dec 2009 Location: Toronto, Ontario	Two round burst I'm not the greatest with gearboxes so hope someone can help me. I decided to reshim my gearbox but after I put everything back together. It started to fire in two round burst in semi time to time. Now it shoots fine but maybe like every 20 shots or more, it fires in two round burst. I was thinking if there was problems with the switch assembly but maybe it's my shim job? I'm using a 9.6 NiMH battery.

June 6th, 2012, 17:19	#2
tunabreath Trader rating Join Date: Dec 2005 Location: Edmonton, AB	If your sector gear is shimmed too low (to the left), it can interfere with the semi-auto cutoff lever. Larger diameter (not thickness) shims on the bottom of the sector gear can also interfere with the cutoff lever. __________________ Vita, Passione e Pistole

June 6th, 2012, 23:44	#4
L473ncy Trader rating Join Date: Oct 2004 Location: 11-30-24-1W5	I've heard of cutoff levers getting worn down on King Arms M4's.... Could that be it? Basically it gets worn down and doesn't always cut off properly. If sector gear shimming is correct try replacing with a known good cut off lever and if it works flawlessly after a stress test then that's your problem. __________________ ಠ_ಠLess QQ more Pew Pew READY TO >> RACE

June 6th, 2012, 18:07	#3
audi_bhoy Trader rating Join Date: Mar 2009 Location: Trois-Rivières	tunabreath got it right !!

June 8th, 2012, 03:13	#5
Eien Trader rating Join Date: Dec 2009 Location: Toronto, Ontario	Maybe I shimmed the sector gear too low.. not sure yet but I will check tomorrow. IIRC, it didn't had the burst in semi issue before I re shimmed it.

June 8th, 2012, 18:52	#6
AngelusNex formerly Sepulcrum Trader rating Join Date: May 2007 Location: Kingston,ON, aka Funkasia	If it's got a weak spring this can happen. friend of mine had this "problem" with his AK, was just cause it was a brand new powerful battery, after a few games it went back to normal as the battery broke in. Though if you have anything above a M90 spring I can't see this happening.

June 8th, 2012, 19:09	#7
Spike Privateer Airsoft Trader rating Join Date: Dec 2008 Location: Beaverbank, NS	I have a 110 spring in my CA and it did the same thing... I switched to a lower voltage battery and it stopped. __________________ I change primaries like other people change socks.

June 9th, 2012, 15:03	#8
Eien Trader rating Join Date: Dec 2009 Location: Toronto, Ontario	I have a M90 spring installed in it but I was only using a 9.6v NiMH battery...

June 24th, 2012, 15:19	#9
karl_azytzeen Trader rating Join Date: Mar 2012	This is an overspin issue. The inertia due to the soft spring /high power motor makes the gears continue moving, despite the motor is not reciving energy (cut of lever works well) This can be solved: 1) using lighter gears, like systema energy done in carbon. 2) stiffer spring 3) less battery voltage 4) (what I choose an the best with springs < 110) Mosfet with active braking.

Two round burst

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