The should not be touching, but should be a little closer then half way in. A good way to adjust the mesh is use the header off of a package ( or thick paper). Tear a strip off (at least as wide as your gears) then place it in between the spur and the pinion. push them together fairly tight, and then tighten your motor mount screws. Pull out paper and you should have proper spacing. Just rotate the spur and make sure the spacing is consistent all the way around (sometimes the spur or pinion may not be perfectly round). There should be just a little movement between the gears, not very much.
What kind of batteries and electrics do you have in your buggy? If the batteries are not up to the task you will have a delay before the buggy accelerates in either direction.