I was mucking around with my char-g cars today, and I decicded to make a fully modified car (i have 6 to modify!)
So I was putting the parts on, soft tyres, 12:1 gearing etc, when, in my 3.0 motor packet, lies a 7t pinion, the very thing to blitz all my mates cars! then, i find the gearing is too tight, it wont move. i tried all my gear sets, and the same thing.
You need to adjust the motor. Try putting it in the 3 o clock poition first, and work your away around until you get a good fit. Mine works in the 2 o clock position.