About two years ago I purchased a custom gun from airsoft gi. The gun was based and built off of a G&G combat machine blowback platform. After a year and a half, the blowback cylinder broke and I disassembled the gearbox. After figuring out the unit was beyond repair, I ordered a new cylinder and re assembled the gearbox. To my surprise the rate of fire was about half the original(15rps - 7rps). I have tested both my 9.6 batteries On my new CQB M4 I got and friends guns, and the batteries are fine. I am lead to believe its the motor but I don't understand how a motor not in use can die. Any help is appreciated!