M-05 Pro - Installing motor

[DCLXVI]

I bought a used M-05 Pro which has (I think) some kind of speed tuned gears, so when I try to install a motor the default holes doesn't seem to line up to get the gear mesh right, does anyone have any info on this or is it me that suck?

[digitrc]

The speed tuned gears are probably from 3Racing. Depending on what spur is fitted inside the car, you'll need to go either 2 or 4 teeth larger than the standard pinion to get it to fit.