yes, one can engrave on bike parts. push graving would be ok for fine detail like shading. hammer & chisel would be better for the main work. for the most part, you'll be doing larger size designs, therefore i'd think the h & c would serve you better. depending on what parts you choose to do, holding the part can be tricky. check the archive-- tira, neo dutch, and others have done bike parts quite nicely. good luck
Welcome to the forum. If motorcycle parts are your interest you DO NOT have to have a air assisted set-up or a engraving vise. They will be helpful at times but to get started you can use Hammer and Chisel, Optivisor, polishing wheel, graver sharpening system of your choice, and a few other niceties.....big thing is can you draw? Create cool designs?
Have you seen these videos? http://www.youtube.com/watch?v=Gu2rB8SMaGU