Right after I swapped out my 44t for a 36t sprocket, without touching anything on the motor....... I go to try out the bike and first off- pretty nice speed. but then when I begin to coast and pull in the clutch, it makes a horrible grinding noise from the motor. If I pull in just a bit, there's no noise. I took off the clutch cover to see if anything seemed abnormal, the only thing i did notice was that the big gear has a good amount of play and that it seems like it's missing a few ball bearings? totally stumped.. please help. thanks.