A few teams had this same issue.
The solution is that there is an inside and an outside to the mounting plate. Our plan was to label the plates so it was easy to tell this, but that did not get done. If the motor was mounted exactly shown on
the document posted on this page, then the gears would mesh much closer together.
Some teams have responded that the gear mesh was a bit too tight when they assembled the Upgrade kit as shown on the assembly instruction document. To fix this, teams made either the 6mm stud hole larger (by 0.020") or by making the the capture bar holes larger (by 0.020"). These larger holes let the Mini-Bike motor gear move away from it's mate.
Andy B.