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WillBurnett

m4 gearbox help needed!

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Hi guys, looking for some help and advice on my m4. I haven't got any pics at the moment but will upload some soon to help with this post.

 

Basically I bought some upgrades for my m4 which is a cyma m4 with a v2 gearbox. As part of my upgrades I put in a gate nano ssr mosfet which required me to solder into a trigger contact. So I stripped my gearbox and soldered the wire in, ran it out smoothly and took my time. Put it back together and give it a shoot and it worked sweetly in semi and full. Then after a few shots it wouldn't shoot but I could hear the motor and gears whir. Naturally I s**t myself thinking I'd stripped all the gears and piston. So I stripped it down again expecting the worst and nothing seemed damaged, I checked all gears under a microscope and nothing. So I re fit everything, making sure the sector gear was aligned correctly, all the shims were in the right place etc, put it back together and the same happened again?

 

I'm completely lost now coz I really can't think what it could be. When it whirs and won't shoot I've noticed that the piston it locked right back, so I'm sort of thinkng that maybe the sector gear has cycled too far and has jumped off the teeth, but that's a wild guess and I'm not sure if that can even happen lol! It is a shitty plastic piston as everything in the gearbox are stock parts.

 

My intentions are to upgrade the gearbox at some point with uprated piston, head, gears, spring etc but don't want to buy all the parts for the same thing to happen. Again sorry I have no pictures to accompany I will try and get some soon. Hope someone can help!

 

Will

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Couple of things I would try is:

- Remove the cylinder, piston and tappet plate and connect just the motor/pistol grip and a battery then see what happens - looking inside, does the sector gear cycle properly?

- Remove the MOSFET from the circuit and try it - what happens? - Could be a fault with the MOSFET.

 

Either way you are going to need to go through a process of elimination and find out what isn't the problem.

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Make sure the piston is lined up in the grooves inside the cylinder properly. I managed to do this reassembling mine at 2am one morning. Piston jams right back and won't release, battery gets dead warm too!

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Sweet guys thanks, plenty to check for! I've given up after spending the majority of today on it, I'll let you know how I get on tomorrow!

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and what position is the anti reversal latch in??

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Ok so after a few days I got to the bottom of the problem! Very, very poor shimming from the place I got it from! Sector gear and bevel gear where doing gymnastics! So bit the bullet and ordered a s**t load of lonex parts to rebuild it with! Thanks for the help though guys wouldn't have found the problem without you!

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Can't really go wrong with Lonex parts...

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