Not sure if a Sport or 3D but same fault can happen!
First the main gear strips.....
If Black then replace for a white version.
If this is striping!
On the older 3d machines and standard on the sport, the pinion from the motor was retained in the top bearing by pressure only, sport and 3d used the same design.
From the factory it was oiled for protection and assembled, seeing it assemble some never stripped. So you had a oiled pinion in a bearing..
It was common that this was not stripped and red locktited in the bearing and because of this the pinion spins quicker than the bearing when reving the engine. so the pinions wears, makes the air gap between the pinion and the main gear too large..http://www.evorc.com/shopimages/pro.../02-3302%20.jpg
Tail gear in the tail box breaks apart...
The pin that fits the gear to the tail shaft is a roll pin, we found the hole drilled in the gear was to small putting load on the gear that it could break. shatter! if factory built only know of two to do it!
Its also possible to cause the same fault when replacing the gear as punching the pin into the shaft spreads the end of the pin craking the plastic.
Think it was a 2mm pin and a 2mm hole in the plastic, was changed to 2.3 in the plastic, i think..
A bad auto can put the gear under load and the next flight bang same fault as the weak link..
You can get a metal version but have found that can go wrong so I carried out this change..http://www.rcheliaddict.co.uk/knigh...ar-fitting.html
The front counter gear on the sport needs to be replaced if black, change to the white, its a must!
hope this helps
(gunnell_s) still owes me money! ... web evorc.com