You asked:

>I have a motor control circuit (H-Bridge) and its powered off 6 volts.
>I am using a pic to control the motors, and my problem is that since I
>am only supplying 5 volts and the control, the motors don't go their
>full speed. How can I fix this.

How about that .... finally a question I'm qualified to answer!  Your
problem statement is not entirely clear to me, so as I understand it:

1. you have a 6 volt motor,
2. you're driving it via  an H-bridge off 5 volt Vcc
3. one side of the motor is biased at 2.5 volts  (the mid point of one side
of the bridge)
4. you are reversing the direction of the motor by pulling the other side of
the bridge high or low with a PIC?

Did I get that picture right?  That being the case, the motor is running
slow because it never sees more than half the 5 volts across the bridge....
that of couse, less the saturation drops of the bridged transistors
conducting at the given time.  If the transistors are in an emmiter follower
config, then you have a fairly large drop across each of them!  A
complementary common emmiter topology for each leg of the bridge would be a
lot better.

You can also:

a) Increase the supply voltage to the bridge, and add some level shifters
between the PIC output and the output transistors to get more swing.

b) with the configuration as a full bridge, control *both* sides of the
bridge with the PIC: drive each side of the bridge in the opposite
direction.  That way you have full potential across the motor less the Vce
drops.... not as good as having 6 volts, but a t least twice what you now  have.

Hope this helps, let me know how it goes.
... Gregg