for the black spots, this is caused by the crappy way firefly does ray-tracing.

this is both effected by the smoothing of polygons and the quality setting on the material.
Mostly the Smoothing of polygons.

turn of "smoothing" under the bike object properties, and see how that effects it. if that doesnt work or doesnt completely fix it, go into the material, and try playing with the quality setting under the reflect node.

for a simple reflect environment that can look quite nice, set your background to black, then add a cloth plain with a scale of around the 3000 mark make it a dark greyish color or some type of flooring.  add a sphere primitive to the scene, scale the z axis to about 500 and the x axis to around the 150-200 mark. scale y to about 25.
set the ambient color of this ball to white, and amient value to 1.

position the ball above the bike but out of view of your render.

this should give you a very nice basic "car render" reflection.

TemplarGFX
3D Hobbyist since 1996
I use poser native units

167 Car Materials for Poser