This isn't at all a bad attempt.... and on first glance actually looks amazing
However there are some areas that need fixing:
-> Bad Selections.... these are particularly noticeable around the arches, - they look very angular instead of the smooth curve that they should be - try and use the pen tool
->The paint has a little too much of one hue and colour, with the strong light source at the front we'd expect a little more variation in the tone
->The roll cage is a solid colour apart from highlights This is the part that lets the chop down most - it just doesn't look like a tube - it needs more shadows down either side and a lighter section in the middle of each bar

On the whole not a bad chop though - cool styling and a nice bg change