problems with m4 gearbox
 

ok. so in short my problem seems to be that the motor is not turning the gears. the motors i have tested both are turning properly but when they are connected to the gearbox it seems as though the motor is being locked up. i can hear it trying to turn but it just wont. the spring in the mechbox was tested at about 350 fps previously so i dont think it is too heavy to be turned. any common problems this could result from? any solutions?

-shimming too tight
-motor set too high
-piston not installed properly
-underpowered or uncharged battery

motor not turning
 

try charging your battery yes it will run w/out load, with load not enough power maybe just charge your battery and test it again.