From the picture, the B4 looks like one of the old RTR B4s.
The motor that came with these were not great, ok for starting off, but no good for racing.
If you're going to go racing, check with your local club, but a good start would be a 10.5t brushed motor.
The
Reedy systems are good units, good for the price if you want to go new.
If you are buying anything at this stage with technology, brushless is the only way to go.
MiCk B. :-)