Version 3 Gearbox lockup & Piston Damage - ICS AK74M

My personal guess is the motor in faulty or way under powered for the spring you have, also as hangtight said motor pinion is too tight try reducing the height of the motor and see if that give a slightly better result as its working way to hard - when you shot the video did you have a spring in the gear box as it do not sound like it fired ? i.e. did not do a full cycle ? in which case take the gearbox apart again and check that then piston is full retracted (when the spring is compressed) that it can release if that make sense. 

 
also when full assembled test the tappet plate by pushing the nozzle and make sure it travels in and out freely 

 
I apologise for bringing up an old post back to life but I literally have this exact same problem.  Did you ever find out what was causing the gear to lock up?

I am of the belief it is the final tooth on the piston not allowing the sector gear to release or that when it does release the piston it rubs against the teeth and the anti reversal latch kicks in locking the gears.

 
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Yes it was eventually diagnosed as a dud motor and once replaced the gearbox came back to life...funny that.  Its been running 11.1 lipo's all year and not a problem.

 
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