Let's get cracking! First things first, you'll want to download the freeware Photoshop (Cs2 I think) and head to Hobby Lobby, use their app 40% off coupon and pick up the WHITE BACKED Testors Decal paper. You'll also need the decal spray bonder which is actually the plastic covering that makes up the decal.
Measure the decal on the bike. Keep making the image size smaller until the decals are the perfect size (print them on regular paper, not your decal paper yet). Make sure you don't resize the photo and keep the dpi the same (uncheck the boxes when asked to reize when you save the file).
Print the decals out and spray the page twice with the bonder. Trim the decals exactly against the image border and dip, slide, apply them like regular decals.