MOPED ARMY

OK so i went through it today… The motor runs great!!!!!, The rear tire spins fine. But it is so noisy , like metal clapping. I took off the right cover and found all the gears, every thing seemed to look great, i put it back together and put new oil in it. So If it is running and i pull in the rear break the rear tire is not moving. But it is still verry noisy, Almost like a major interanl vibration. Any ideas ? Cant be from the drive unit because its not turning with the break in ./..