First I don’t get it what kind of motor it is! Is it with Carburetors or injection, if it’s a carburetor you should have throttles inside the scoop! If injection no scoop. The tubes between the scoop and engine are to long, put the scoop direct on engine instead. Belt wheel and screws need more details.
I guess the motor is in chrome or polished aluminum, the color should be more distinctive and sharps lines between the colors. You should use more skyblue, green and brown. Look at the chrome parts in front, that’s what I mean! Add two engines I found, these describe better then my word!
http://www.flickr.com/photos/ebraheemalabdulla/4338845768/
It’s the same with front rim chrome, it doesn’t look real.
Maybe I’m wrong, this is what I think!
Don’t miss consider me, I really like your chop.