Looks like you've using the wrong measurement. The 6.2cm / 2.4" measurement is the Bottom Bracket Drop. This is the vertical distance from an imaginary line intersecting the axles of each wheel down to the center of the bottom bracket.
Find many great new & used options and get the best deals for 52V Electric Motor 1000W Mid-drive Kit BBSHD 68mm Bottom Bracket Bafang at the best online prices at eBay! Free shipping for many products!